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Great News From Liberia

The news from Liberia is wonderful: the last known Ebola patient has been discharged from treatment! [NYT 3/6/15] This doesn’t make Liberia “Ebola free” – that requires 42 days (twice the incubation period) with no new cases. Many contacts are still being monitored, and others may not have been identified, so Liberia may still have to deal with a few more local outbreaks before it can declare victory. Also, so long as Ebola continues in neighboring countries the disease may be brought back to Liberia by travelers (though note this heartening item about an effective Liberian border control operation: [IOM 2/4/15]). And the risk of an unrelated jump to a human from an animal reservoir will continue indefinitely. Nevertheless, this is a moment to be savored!

Update 3/24/15: A new patient has been identified in Liberia, who probably was infected by her boyfriend, an Ebola survivor. [NYT 3/24/15]. This is disappointing, but the fact that only one instance has come to light suggests that this mode of transmission is rare.

Ongoing Transmission in Sierra Leone and Guinea

Sierra Leone initially showed a similar pattern of precipitous decline in patients, but since the end of January weekly cases have stabilized between 60 and 100. [WHO 3/4/15] This is better than exponential growth, but it’s not on track to ending the epidemic. Guinea didn’t have as sharp a peak, but it also hasn’t experienced such a dramatic improvement: about 50 cases are continuing to arise each week. In both countries the steady rate of new cases implies an Effective Reproduction Rate of about 1. Pushing this down just a little would eventually end the epidemic, while letting it rise would allow exponential growth to resume. Liberia has shown that it’s possible to snuff out the epidemic, but Sierra Leone and Guinea are not yet following in Liberia’s footsteps.

I don’t claim to know how Liberia did it, but somehow the Effective Reproduction Rate dropped to about 1 in September, then fell much lower from October on. Sierra Leone’s peak and fall were similar, but occurred about two months later, and the decline has now leveled out. While the opening of new treatment centers certainly helped in recent months, my own best guess is that the main factor in both countries is that people simply “got religion.” That is, a large enough fraction of Liberians came to accept that Ebola is caused by a virus, not a curse; that people who fall ill need to be cared for in safe settings, rather than at home; and that corpses need to be handled with extreme care. I suppose that a comparable fraction of Sierra Leone’s population reached similar conclusions, but the epidemic is now continuing there and in Guinea within sub groups that haven’t fully accepted the message.

Devilish Details

The last Ebola patient in Liberia, Beatrice Yardolo, came from a worrisome cluster of cases “in a community called St. Paul’s Bridge, located in what was one of the biggest Ebola hot spots in Monrovia, New Kru Town.” [NYT 3/6] The New York Times reported that, “[t]he outbreak was unusually violent and far-reaching, in part because it involved criminal gangs that did not cooperate with the authorities and fears that it could be spread through a knife fight with one member nicknamed Time Bomb.” Even more troubling was the fact that known contacts on several occasions left Monrovia for other parts of the country. [FrontPageAfrica 2/3/15] One of the escaped contacts died in Margibi County, and required the tracking of 256 contacts there. [GNN Liberia 2/4/15]

Ebola came into the Yardolo family from Beatrice’s cousin Steve, who probably became infected at an Ebola treatment center where he worked. [AllAfrica 3/6/15]  Steve infected several other members of the family, eventually including his daughter Amanda. Beatrice took responsibility for Amanda’s care, but again and again Amanda was mis-diagnosed and rejected from Ebola treatment centers. Beatrice was left responsible for bathing and otherwise caring for her. After Amanda died Beatrice went immediately to a treatment center started showing symptoms, which probably saved her life.

Ebola didn’t end in Liberia because people behaved well, but because the strategies of isolation and contact tracing worked despite much bad behavior and many mistakes.

Sierra Leone’s experience is vividly described in another New York Times piece. [NYT 2/18/15] The epidemic was re-ignited by three sick fishermen who landed in a poor area of Freetown in early February. Two dozen people in the area ended up contracting Ebola from this initial group before transmission was brought under control. A quarantine was imposed but was frequently broken. One shopkeeper fell ill but was afraid to go to a hospital in Freetown. Instead he broke quarantine and traveled three hours to his home village, where he visited a traditional healer, then died. He caused the infection of some 42 people in the district.

Endemic Ebola?

Ebola is still being actively transmitted in Sierra Leone and Guinea, and may yet recur in Liberia, or spread to other countries. But the Liberian experience gives every reason to hope that the techniques that worked there can eventually end this epidemic altogether. The possibility must be acknowledged, however, that the epidemic will continue indefinitely, neither growing exponentially nor definitively ending. In this case Ebola would become “endemic” to West Africa — just one of the typical diseases that people get there. I can’t disprove this — indeed it seems to be happening now in Guinea — but I have several reasons for doubting that this will happen with the current strain of Ebola:

  • It’s too deadly. A cluster of a less lethal disease might go relatively unnoticed, but this can’t happen with Ebola. The deaths of family and friends, one after another, cannot be ignored. The presence of Ebola in a community will not be tolerated for long.
  • Its incubation period is too short. A disease that takes months or years to emerge (e.g. AIDS, leprosy, tuberculosis) can hide in a human population, but Ebola emerges quickly, or not at all.
  • It’s only transmitted from person to person. Aside from the wild animal reservoir (discussed below) Ebola appears to be transmitted only from person to person. A disease that could also infect some more familiar animal, like fleas or rats, could hide in the animal reservoir and reemerge unpredictably. Fortunately, Ebola shows no sign of doing this.
  • It’s only transmitted by direct contact. Fortunately, Ebola isn’t airborne; it’s transmitted only by direct contact with bodily fluids or contaminated surfaces. This makes contact tracing and isolation so effective. It’s much more difficult to contain a disease like the flu that spreads through the air.
  • People are infectious only when they are ill.  Update 3/24/15: (except for the semen of male survivors). There is no indication that there are “Typhoid Marys” who can transmit Ebola without themselves falling ill, except for one instance in which a male survivor appears to have infected his partner, presumably through semen, which is known to contain Ebola virus for several months after recovery. [NYT 3/24/15] This will make the disease a bit more difficult to eradicate, but is not cause for panic. As noted above, the fact that just one infection of this type has come to light suggests that this mode of transmission is infrequent. Additionally, now that an example exists one might expect many “discordant couples” (in which the male is a survivor and the female is not) to use condoms, which should further reduce the risk. One question that calls for further research is how long the virus can persist in the semen of a male survivor, and whether a negative semen test is sufficient to make unprotected intercourse safe for the survivor’s partners.

For these reasons I think it’s highly unlikely that Ebola will become endemic based on human-to-human transmission (absent mutation). So long as we don’t lose focus I expect that Sierra Leone, and eventually Guinea, will be able to end this epidemic using the standard techniques of contact tracing, isolation, funeral management and education.

The Wild Animal Reservoir

In one important respect Ebola already is endemic to East Africa: For forty years it has jumped every few years from its wild animal reservoir (probably fruit bats) into a human population. Just this year an unrelated Ebola outbreak in a rural area of Uganda flared briefly and was extinguished. [CDC]  There is every reason to expect this pattern to continue, since:

  1. even when we have a vaccine it will never be feasible to vaccinate the entire relevant population,
  2. contact with infected animals such as bush meat may be reduced through education but can’t be prevented altogether, and
  3. there is no conceivable way to eliminate Ebola from the animal reservoir.

This is too bad, but it’s a bearable situation, since most outbreaks start in remote rural areas, where they can be quickly snuffed out so long as they are detected early and the response is competent and decisive.

So far as we know the West African epidemic arose from a single jump between a wild animal reservoir and a human. There might be some reason why this was an isolated incident that won’t recur. But it seems much more likely that Ebola is now established in a West African animal reservoir, from which it will now jump periodically into humans, the same way it has for decades in East Africa. After the current epidemic is brought under control it will be essential for all West African countries to establish systems for early detection of new Ebola outbreaks, as has long been the case in East Africa.

We’re lucky that infective contacts between humans and the wild animal reservoir are so rare. If Ebola became established in an animal population that lived in closer contact with humans — rats, pigs, or even dogs — animal-human transmissions could be much more frequent. There is no evidence, however, that this is happening. Genetic evidence continues to indicate that the entire West African epidemic was sparked by a single animal-human transmission in Guinea, from a bat to a 2-year-old boy.

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Ebola is obviously much less contagious than airborne viruses like influenza, and much more contagious than some other viruses, such as HIV, the virus which causes AIDS. What can we say at this point about how contagious Ebola really is?

The Official Statements

Through mid-September the WHO’s web page included this unfortunate paragraph, which is still widely quoted:

The risk of Ebola transmission is low. Becoming infected requires direct, physical contact with the bodily fluids (vomit, faeces, urine, blood, semen, etc.) of people who have been infected with or died from Ebola virus disease (EVD). [WHO 9/16/14]

As of September 20 this language had disappeared, and WHO’s current fact sheet has a more detailed and sobering description of how Ebola is transmitted between people:

Ebola … spreads through human-to-human transmission via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids.

Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced.

Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola.

People remain infectious as long as their blood and body fluids, including semen and breast milk, contain the virus. Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness. [WHO 9/19/14]

The U.S. Centers for Disease Control (CDC) Transmission web page roughly parallels WHO’s fact sheet:

When an infection does occur in humans, the virus can be spread in several ways to others. Ebola is spread through direct contact (through broken skin or mucous membranes) with

  • blood or body fluids (including but not limited to urine, saliva, feces, vomit, and semen) of a person who is sick with Ebola
  • objects (like needles and syringes) that have been contaminated with the virus
  • infected animals
  • Ebola is not spread through the air or by water, or in general, food. However, in Africa, Ebola may be spread as a result of handling bushmeat (wild animals hunted for food) and contact with infected bats.

Healthcare providers caring for Ebola patients and the family and friends in close contact with Ebola patients are at the highest risk of getting sick because they may come in contact with infected blood or body fluids of sick patients.

During outbreaks of Ebola, the disease can spread quickly within healthcare settings (such as a clinic or hospital). Exposure to Ebola can occur in healthcare settings where hospital staff are not wearing appropriate protective equipment, including masks, gowns, and gloves and eye protection. …

Once someone recovers from Ebola, they can no longer spread the virus. However, Ebola virus has been found in semen for up to 3 months. People who recover from Ebola are advised to abstain from sex or use condoms for 3 months. [CDC 9/20/14]

This post will try to tease out what these texts mean, and how well they square with the way in which the West African epidemic has developed. Public information needs to be clear, simple and not dangerously misleading. But it also tries to avert panic; it isn’t always the “whole truth.”

Reading Between the Lines

Both WHO and CDC state that contact with bodily fluids, etc. must be “(through broken skin or mucous membranes).” Apart from a cut this refers to the mouth, nose, eyes and anal and genital openings. What neither statement emphasizes is the importance of the hands as a means for the virus to get to a mucous membrane. A touch to the lips or the eye with a contaminated hand could do the trick, as could also a stray droplet of any sort of bodily fluid.

The examples given of contaminated surfaces differ oddly between the two descriptions. WHO mentions “bedding and clothing” while CDC mentions “needles and syringes.” Both obviously have the potential for transmission. Possibly the WHO fact sheet is directed to individuals while the CDC was thinking more about healthcare providers.

The CDC fact sheet says that “Ebola is not spread through the air.”

  1. It is obviously possible for someone to be infected by a droplet that passes “through the air” onto a mucous membrane. Various experiments have shown such transmission between animals in a laboratory setting. CDC acknowledged this in an earlier fact sheet, but explained, “While all Ebola virus species have displayed the ability to be spread through airborne particles (aerosols) under research conditions, this type of spread has not been documented among humans in a real world setting, such as a hospital or household.” [CDC 4/9/10]
  2. Ebola is obviously not spreading through the air anywhere near as easily as flu. This is the current phrasing of the CDC guidance for managing ill airplane passengers that originally was cited as evidence that the CDC believed in airborne transmission: “Ebola does NOT spread through the air like flu.” [CDC 9/20/14]
  3. The key question is whether Ebola is in fact being transmitted during the current epidemic through the air, and if so how significant this mode of transmission is, and how much it is affected by the condition of the patient. We’ll consider this further below.
  4. Mutation could in principle affect contagiousness by air, and we must remain vigilant about this possibility.

WHO advises that men use condoms for 7 weeks after recovery, while CDC recommends 3 months. That’s a pretty big difference! The Public Health Agency of Canada states that, “Ebolavirus has been isolated from semen 61 to 82 days after the onset of illness, and transmission through semen has occurred 7 weeks after clinical recovery.” [PHAC 9/20/14] This would seem to be a situation in which WHO is minimizing a risk that might exist for more than 7 weeks. At the moment sexual transmission by survivors is the least of our worries, but it may become important in the final phase of ending the epidemic.

The West African Experience

The current epidemic has provided a treasure trove of information about how Ebola does — and doesn’t — spread. Hopefully someone is collecting as much of this information as possible for scientific analysis. Only a few specific cases have been well enough described in the press for any conclusions to be drawn by outsiders, however. While anecdotal, they are nevertheless highly suggestive. For this purpose we are as interested in who didn’t get infected as in who did.

The Super-Spreader Funeral

All cases of Ebola in Sierra Leone have been traced to 14 women who were infected at the funeral of a traditional healer in Guinea. [NYT 8/28/14] It is customary at traditional funerals for people to wash, touch and even kiss the body, so it’s not surprising that they were infected. What’s interesting is that dozens of people attended the funeral — presumably quite a few more than the 40 who agreed to give blood samples — and it’s reasonable to suppose that many of them also had contact with the body. The corpse was clearly quite infectious, but even so it infected only perhaps 1/4 of those who attended the funeral.

The Nigerian Outbreak

Patrick Sawyer was a sociopath who caused the death of a dozen people, and very nearly unleashed Ebola on the most populous country in Africa. [EbolaStrategy 8/31/14] He was also a naturalized American citizen, and the Coordinator of the Economic Community Of West African States (ECOWAS) Unit of the Liberian Finance Ministry. [Note: Nigeria reported a total of 19 Ebola cases. I’ve been able to identify only 14 from the press. The others may be secondary infections plus a handful of additional primary infections, but they don’t much change the picture painted below. I’ll update this post if I’m able to sort out this discrepancy.]

Princess

The story begins with Sawyer’s sister, known as Princess, who was bleeding uncontrollably when her fiancé brought her to St. Joseph Catholic hospital in Monrovia. Her symptoms were recognized and hospital staff initially refused to touch her, but the Chief Administrator of the hospital, Brother Patrick Nshamdze, decided to treat her as if she presented a simple case of a miscarriage. [NationalChronicle 7/29/14] [FrontPageAfrica 8/13/14] Princess continued to bleed, however, and she was about to be moved to an isolation ward when Sawyer arrived. “He insisted that she be given a private room and plunked down $500 to secure it. He proceeded to personally change her gown and placed her in a wheelchair for the move. He was seen to get her blood on his own clothes as well as his shoes in the process.” [DailyBeast 8/14/14] Princess died on July 7. Understandably, Sawyer, Nshamdze and other healthcare staff who treated her without precautions became infected. Then the same thing happened when Nshamdze himself fell ill – doctors, nurses, a social worker and a lab technician fell ill. There’s no special information about contagiousness here, however, since there was lots of blood and few precautions.

Patrick Sawyer

Because of close contact with his sister, Sawyer was monitored daily and told not to leave Liberia. On July 20, after he began showing serious Ebola symptoms, including fever and vomiting, he got on a plane to Lagos, Nigeria, with a layover in Togo, as part of a nine-member ECOWAS delegation to a conference. He vomited repeatedly during the flight, then collapsed in Lagos airport. He was helped into a taxi and taken to First Consultant Hospital, where he initially told the medical staff that he had malaria and denied contact with any Ebola cases. Only two days later was he tested and found tentatively positive for Ebola, at which point he was quarantined.

One of the nurses who treated him, Obi Justina Ejelonu, became infected even though: “I never contacted his fluids. I checked his vitals, helped him with his food (he was too weak). … I basically touched where his hands touched and that’s the only contact. Not directly with his fluids. At a stage, he yanked off his infusion and we had blood everywhere on his bed … But the ward maids took care of that and changed his linens with great precaution.” Another hospital source “told [Front Page Africa] that in addition to yanking the infusion tubes, Sawyer took off his pants and urinated on the floor as nurses fled from his presence.” [FrontPageAfrica 8/11/14] He died five days later, on July 25.

A doctor who treated him, Dr. Ada Igonoh, also became infected. She gives an extremely detailed account of Sawyer’s stay at her hospital (and of her own illness and recovery) in a moving Front Page Africa article. [FPA 9/18/14] She felt that, “my contact with Sawyer was minimal. I only touched his I.V. fluid bag just that once without gloves. The only time I actually touched him was when I checked his pulse and confirmed him dead, and I wore double gloves and felt adequately protected.” The first several days in which Sawyer was treated for malaria without full precautions could explain her infection, however, as well as that of Dr. A.S. Adadeveoh, who treated Sawyer during the same period. [FPA 8/25/14]

“In total, Sawyer reportedly came in direct contact with 59 persons, 44 of whom were at the hospital… Sawyer came in contact with three ECOWAS officials – a driver, a liaison officer and a protocol officer. Also in the list are two nursing staff and five airport handlers.” [FrontPageAfrica 7/31/14]

Out of all his 59 contacts Sawyer appears to have directly infected just 5 people: The nurse and two doctors already mentioned, an ECOWAS official who picked Sawyer up at the airport and took him to the hospital, and an ECOWAS diplomat who was part of the group who greeted him on his arrival. All his other contacts did not get infected. That includes both passengers and crew on two flights, during which he was repeatedly vomiting, and everyone else in the Monrovia, Togo and Lagos airports. He was capable of infecting others, obviously, but on balance Sawyer was not very contagious.

The ECOWAS Diplomat

The ECOWAS diplomat escaped from quarantine in Lagos on July 26, traveled to Port Harcourt, and arranged to receive secret treatment in a hotel room by a local doctor, Iyke Enemuo. The diplomat recovered but the doctor was infected. There’s no indication that any other contacts of the diplomat were infected, however, so once again the healthcare providers bear the brunt of transmission. Apart from infecting Enemuo, the ECOWAS Diplomat was not very contagious.

Dr. Iyke Enemuo

Dr. Enemuo was yet another sociopath, following in Patrick Sawyer’s footsteps. He kept his contact with the infected ECOWAS diplomat secret and continued to pursue an active medical practice and social life, even after falling ill. WHO recounted the shocking details (apologies for the duplication from my first post):

After onset of symptoms, on 11 August, and until 13 August, the physician continued to treat patients at his private clinic, and operated on at least two. On 13 August, his symptoms worsened; he stayed at home and was hospitalized on 16 August. Prior to hospitalization, the physician had numerous contacts with the community, as relatives and friends visited his home to celebrate the birth of a baby.
Once hospitalized, he again had numerous contacts with the community, as members of his church visited to perform a healing ritual said to involve the laying on of hands. During his 6 day period of hospitalization, he was attended by the majority of the hospital’s health care staff.
On 21 August, he was taken to an ultrasound clinic, where 2 physicians performed an abdominal scan. He died the next day.
[WHO 9/3/14]

Nigeria had to track some 255 contacts, 60 of whom had high-risk or very high-risk exposure!

Of all those many contacts, Dr. Enemuo actually infected only 5 people: his wife (also a doctor), his younger sister, a doctor who treated him at the hospital, a pharmacy technician, and an older woman who shared his hospital room. [NigeriaTimes 9/19/14]  [Reuters 9/1/14]  He was certainly capable of infecting people, but considering the number of people he was in contact with after falling ill, Dr. Enemuo was not very contagious. Once again, caregivers and immediate family members were at greatest risk.

The Senegal Student

A 21-year-old college student was under observation in Guinea because he had helped care for several family members who had fallen ill with Ebola. Nevertheless, he traveled in a six-passenger vehicle to Dakar, Senegal, arriving on August 20. He stayed with his uncle in a crowded household for three days, then went to a local hospital, but did not mention his exposure to Ebola. He was initially sent home, but the following day “the Guinean health services reported ‘the disappearance of a person infected with Ebola who reportedly traveled to Senegal,’ according to Senegal’s health minister,” and the student was quarantined. [BBC 8/29/14] [Bloomberg 8/31/14] 67 close contacts were placed under observation: people he was in contact with during his journey, members of his uncle’s extended household, healthcare providers at the hospital, etc. [WHO 9/12/14]

The striking feature of this case is that none of the student’s 67 close contacts became infected! This is very different from other situations. My best guess is as follows: The student was never terribly sick, and has fully recovered. Consequently, he may not have had the same viral load as other patients, and may not have been throwing off bodily fluids as prolifically. It’s also possible that the main hospital in Dakar follows more rigorous universal precautions than those in the other affected countries. Whatever the reason, this is a striking instance of how non-contagious Ebola can sometimes be.

Healthcare Providers

More than 240 healthcare providers have been infected during the West African epidemic, half of whom have died. [WHO 8/25/14] The great majority were local doctors and nurses who did not wear full protective gear, often because they were not yet aware that a patient had Ebola and sometimes because of a shortage of supplies. In a few cases, however, healthcare providers who were apparently following standard procedure nevertheless became infected. These cases raise concerns about the mode of transmission.

Dr. Kent Brantly

Brantly became infected working with patients at a Monrovia hospital operated by evangelical Christian organization Samantha’s Purse. He asserts that he followed all CDC recommended procedures, including wearing a standard N-95 face mask, the type also used by Médecins Sans Frontières/Doctors Without Borders (“MSF”).  [MSF 7/28/14]  This raises a question of whether Brantly was infected by airborne droplets that passed through his mask. This point is pressed in a tendentious but interesting article, written by a doctor who argues that Ebola healthcare providers should use the more expensive and uncomfortable P-100 (HEPA) face masks to fully protect against airborne droplets. [AmericanThinker 8/24/14]

The N-95 mask is designed to block 95% of “solid and water-based particulates (i.e., non-oil aerosols)”. The P-100 (HEPA) face mask blocks 99.97% of particulates and aerosols, whether or not oil-based. [CDC Jan, 1996]

  • Maybe Brantly made some other mistake, of which he wasn’t aware. This seems frighteningly possible, with the odds of an error — small though they may be — relentlessly adding up as he worked day after day in close contact with Ebola patients.
  • Maybe airborne transmission is indeed very rare, but Brantly got unlucky.
  • Maybe airborne transmission is easier than we have thought, and MSF has been very, very lucky.
  • Maybe the virus has mutated to become more easily transmitted by air — though obviously still vastly less easily than the flu.

The French MSF Volunteer

MSF announced on Sept. 17 that a French volunteer at one of its treatment centers in Monrovia had become infected, despite their strict infection-prevention protocol. She is the first international MSF staff member to be infected in the West African epidemic, although 7 local staff members had previously fallen ill, out of more than 2,000 MSF staff members in the region. The treatment center is turning away new patients pending an investigation into how the volunteer became infected. [Reuters 9/17/14]

From one perspective eight people out of 2,000 is less than half of one percent. But, as MSF President Joanne Liu had previously pointed out, the entire control effort can fall apart if healthcare providers feel personally unsafe.

We have no further information about how this volunteer may have been infected, but the announcement of the MSF investigation implies that it wasn’t due to anything obvious. Airborne transmission is a possibility.

The American Journalist

Added 10/6/14: An American journalist, Ashoka Mukpo, tested positive for Ebola on Oct. 2. He believes that he may have become infected when he was splashed while spray-washing a car in which an Ebola patient had died. [ABC 10/6/14]  This seems credible and consistent. He is, by the way, being treated in the high-level biocontainment unit at the University of Nebraska Medical Center. This unit is the largest of four U.S. biocontainment units, and has 10 beds, which means that the U.S. has a total of less than 40 bio-containment beds in the entire country. Hmm…  [NPR 10/6/14]

Ebola Transmission in the Developed World

At this writing there have been only two instances of transmission of Ebola outside of Africa, both involving nurses who cared for Ebola patients in the last stages of the illness. Both wore full anti-infection gear; this is not like the West African cases in which healthcare providers were infected before precautions started being taken, or because proper gear wasn’t available. Both nurses — at least initially — said they were not aware of any breach of the anti-infection protocol.

The Spanish Nurse

Added 10/6/14: A nurse (more precisely, a volunteer auxiliary nurse) contracted Ebola while treating a Spanish missionary in Madrid’s Carlos III hospital, where he died on Sept. 25. She is the first person known to have contracted Ebola outside of Africa. Reportedly she only entered the patient’s room twice, once after his death. [NYT 10/6/14] We have no information about what precautions the nurse used, and whether a mistake may have been made. Update 10/8/14: The nurse initially said that she had followed the anti-infection protocol to the letter, which would have undermined confidence in the protocol and increased the anxiety of healthcare personnel. She then said that she “might have” touched her face with a contaminated glove as she was taking the protective suit off. [NYT 10/8/14]  It’s reassuring — if also a bit too convenient — to have an explanation for how the nurse was contaminated.

The infection of the Spanish nurse is worrisome but not inconsistent with the experience in Africa, where hundreds of healthcare workers have contracted Ebola, and several Western medical personnel have been infected without noticing a failure of protocol. We do need to figure out why this is happening, but the extreme infectiousness of corpses and people in the last phase of the disease is known, and there’s nothing about this case which changes the picture.

The real issue in her case has nothing to do with contagion: it’s the fact that Spain took nearly a week to test her for Ebola after she reported that she was running a fever. This casual attitude will have to stop! Western countries have ample resources to contain Ebola, but it will bite anyone who treats it with laziness or contempt.

The Dallas Nurses

Added 10/14/14: Nina Pham, a Dallas nurse who gave extensive care to Thomas Eric Duncan throughout his hospitalization is the first person known to have contracted Ebola in the U.S. As noted above, she was not aware of any breach of protocol. This is of course worrisome, and affords further evidence that the CDC needs to focus more closely on the protocol, and the way in which training is given. But it isn’t a new issue. [NYT 10/13/14]

Again, the important issue isn’t contagion, but the fact that Ms. Pham wasn’t monitored as a contact. Fortunately, she self-monitored, detected a low-grade fever, and had herself admitted to the hospital. She tested positive for Ebola on the evening of 10/11.

Added 10/20/14: A second nurse who treated Duncan, Amber Joy Vinson, was confirmed as having contracted Ebola on Oct. 15. She had been self-monitoring and had reported a low grade fever, but was nevertheless allowed to fly to Cleveland on Oct. 10 and back to Dallas on Oct. 13. That was obviously stupid, and put at minor risk a large number of people in both cities and on both flights. But once again, the fact that an inadequately trained and protected nurse got infected from a later-stage Ebola patient is nothing new. [NYT 10/20/14]

Added 10/29/14: Both nurses have now been declared Ebola-free and discharged from hospital.

The Other Contacts of Thomas Eric Duncan

Added 10/8/14: It’s too early to say, but the fact that none of Duncan’s other contacts have yet shown symptoms is notable. He was very ill before being taken to the hospital the second time, and lived in close quarters with his girlfriend, her son, and her two nephews. He wasn’t as sick the first time he went to the hospital, but it seem clear that several doctors and nurses were in contact with him without taking exceptional precautions. It would be a remarkable confirmation of how infectious Ebola isn’t if all of these folks escape infection.

Added 10/20/14: Happily, nearly all of the 50 contacts with Duncan before his second hospitalization have now completed their 21-day quarantine period, with no Ebola symptoms! As well as being great news for them and for Dallas it confirms once again that Ebola is remarkably noncontagious until the final stage of the illness. Dozens Declared Free of Ebola Risk in Texas [NYT 10/20/14].

One nuance doesn’t change this conclusion, but could lead to a further little outbreak: As noted below, 5% of people infected with Ebola don’t show symptoms until more than 21 days from exposure. [NEJM 9/23/14]  If someone released from quarantine turns up with symptoms after the 21-day period CDC might end up with egg on its face, and public confidence could be seriously eroded. I understand why 21 days has been chosen as a way of sending a simple message to the public but taking this approach is a somewhat risky strategy.

The Contacts of the Dallas Nurses

Added 10/29/14: Nina Pham apparently had only a few contacts, chief among them being her boyfriend. Amber Joy Vinson, however, flew to Cleveland and — after reporting a low-grade fever — back to Dallas. Vinson accordingly placed at theoretical risk a large number of people. It will be interesting to see whether any of these contacts became infected. My own guess — based on the other cases described above — that nobody else will come down with the disease based on contact with either of the nurses. If so, that should alleviate the public’s anxieties, but probably won’t.

The Bottom Line

Here are a few concluding observations:

  • Even though the epidemic is growing exponentially, the individual cases we’ve been able to review support the official position that Ebola is not very contagious, and generally requires contact with bodily fluids or contaminated surfaces. Even a corpse only infected about a quarter of the attendees at a traditional funeral in which touching the body was customary.
  • Caregivers and immediate family members are at highest risk, and others are at relatively low risk.
  • Infectiousness depends on how ill the patient is, both from the perspective of viral load and the amount and character of emitted bodily fluids. There is no evidence of transmission before the patient becomes symptomatic; very little evidence of transmission before the last stage of the illness; but a high risk of transmission to caregivers and others who have direct contact with a patient during the last stage of illness.
  • It isn’t clear to what extent the virus can be transmitted through the air, but:
    • Casual contact such as sharing an airplane or even mingling in a social setting rarely or never seems to be enough to infect. Added 10/20/14: As noted above it’s astonishing that Duncan’s girlfriend and the three boys who also shared the apartment where Duncan stayed avoided infection.
    • Something is infecting healthcare providers, even when they believe that they are following CDC guidelines. It is urgently necessary to determine why so many healthcare personnel who claim to be following CDC procedures are getting infected. We have to figure out what’s happening with that and fix it, whether or not it involves airborne transmission.

Update 10/3/14: A survey article by the WHO Ebola Response Team in the New England Journal of Medicine provides a lot more information, although it doesn’t greatly change our understanding of the situation. [NEJM 9/23/14]  Here are a few key points:

  • The mean incubation period is 11 days, and 95% had symptoms within 21 days of exposure, the recommended period for follow-up of contacts. Accordingly, 5% of infected contacts will first present symptoms after follow-up ends.
  • The article estimates the current effective reproduction numbers at 1.81 in Guinea, 1.51 in Liberia and 1.38 in Sierra Leone. This basically means that each infected person is infecting on average between one and two more people, thus causing the epidemic to grow exponentially. See my earlier post, The Ebola Chain Reaction, for a more detailed explanation. The article rather cheerfully comments that : “This means that transmission has to be a little more than halved to achieve control of the epidemic and eventually to eliminate the virus from the human population. Considering the prospects for a novel Ebola vaccine, an immunization coverage exceeding 50% would have the same effect.”
  • Without changes in control measures, their estimated doubling times range between 15 days for Guinea and 30 days for Sierra Leone.
  • Case fatality has been 70% in Guinea, Liberia and Sierra Leone, in contrast with earlier reports closer to 55%. It was lower in Nigeria but the number of patients was so small that this might be a fluke.

Also, here’s a very clear statement, in the Oct. 2 New York Times, of what is considered “direct contact” with the bodily fluids of an Ebola patient: Understanding the Risks of Ebola, and What ‘Direct Contact’ Means

Update 10/8/14: An article in the LA Times collects questions about whether Ebola might be more contagious than is currently believed: [LA Times 10/7/14]

  • Mutation is of course a wild card, which could make the virus somewhat or much more contagious. This is one of several good reasons for devoting resources to stopping the epidemic as soon as possible. But I don’t see any evidence of significant change in contagiousness, and nobody is claiming specific evidence of relevant mutations.
  • What we do see is a pattern of poorly-explained infections of healthcare providers, especially when patients are in the last stage of illness. This might involve small highly-infections droplets passing through the air, and conceivably might lead to further tightening of the anti-infection protocol. Added 10/14/14: In any case one must welcome CDC’s plan to improve training and to send a team to any hospital treating an Ebola patient. [NYT 10/13/14]
  • What we do not see is large numbers of infections of people who have casual contact with patients, or who have contact with patients before they have become symptomatic. So long as that pattern holds Western nations should have little difficulty keeping Ebola under control, so long as they treat it with the great respect and vigilance that it deserves.

Update 3/24/15: Liberia has identified a single Ebola patient who appears to have been infected by her partner, a male survivor. [NYT 3/24/15]  This presumably came through his semen, which is known to contain Ebola virus for several months after recovery. This will make the disease a bit more difficult to eradicate, but is not cause for panic. The fact that just one infection of this type has come to light suggests that this mode of transmission is infrequent. Additionally, now that an example exists one might expect many “discordant couples” (in which the male is a survivor and the female is not) to use condoms, which should further reduce the risk. One question that calls for further research is how long the virus can persist in the semen of a male survivor, and whether a negative semen test is sufficient to make unprotected intercourse safe for the survivor’s partners.