More than 80 people are now suspected to have been in contact with the first US Ebola case. ABC News says “the number of people who came into contact with Texas Ebola patient Thomas Eric Duncan has zoomed from as many as 18 to 80, health officials in Texas announced in a statement today.” That number probably does not include those he came into contact with earlier, as it transpired that “he flew on two airlines, took three flights, and had lengthy airport layovers – including one at Washington Dulles International Airport – before reaching Texas on Sept. 20.”
And just now the count has clicked up to perhaps 100 persons exposed, according to the NYT.
Not to worry, say the Feds because only actually sick people are contagious. “The Metropolitan Washington Airports Authority and various federal health agencies maintained late Wednesday that other passengers on the flights were at no risk of infection because the man had no symptoms at the time of his trip.”
This is the standard screed. Tom Skinner of the CDC said “I want to underscore that Ebola poses little risk to the U.S. general population. Transmission is through direct contact of bodily fluids of an infected person or exposure objects like needles that have been contaminated with infected secretions. Individuals who are not symptomatic are not contagious.”
Under this model of transmission, those who attend to the sick are in the most danger. Thus, doctors, nurses, attending family members and Good Samaritans are at greatest risk unless provided with protective clothing. Helping out is what got patient zero Thomas Eric Duncan infected in the first place.
It appears an act of compassion led Thomas Eric Duncan to contract Ebola, and become the first patient diagnosed with the deadly disease on U.S. soil.
Just four days before he boarded a plane bound for Dallas, Texas, Duncan helped carry his landlord’s convulsing pregnant daughter to a Liberian clinic to be treated for Ebola, the New York Times reports.
That’s the theory anyway. There’s some difference of opinion about whether only symptomatic individuals are contagious. The basic objection raised is that the boundaries around symptomatic are fuzzy, that there remains some residual chance that pre-symptomatic and post-symptomatic individuals can still pass on the disease, albeit with a lower probability. Science Blogs says, for whatever it’s worth:
According to the usual sources (WHO and CDC for example) the following is probably true. When someone gets Ebola, typically, after a while they get sick. This means they show symptoms. If they did not show symptoms they would not be “sick” even if the virus was in them and even if the virus is multiplying in them. Presumably people are infected with a sufficient number of viroids that they become a host for the disease, the virus starts to multiply above some level that makes the person sick, and we can say at that point that they “have Ebola.” This is when the infected person is able to transmit the disease to others through bodily fluids that might come into contact with wounds or mucous surfaces in the downstream patient.
This is what the WHO and CDC literature on Ebola says, and this has lead bloggers and news outlets to state incorrectly that Ebola is only transmitted to others when the person shows symptoms. Unfortunately this is not true in one or possibly two ways.
It appears that people who have had Ebola, live, and get “better” (i.e., their symptoms go away) can still carry Ebola for a period of time, and in this state, they can still transmit it. What has probably happened is their immune system has started to fight the virus enough that it is attenuated in its effects, but it isn’t’ entirely gone yet. Medical personnel like to send someone home only after the virus has cleared. Even so, men who are supposedly virus free by that standard, when sent home after surviving Ebola, are told to avoid sex for several weeks because there is still the possibility of sexual transmission of the virus. Meaning, of course, that the virus is still knocking around in some individuals at this point, and still transmittable. It is not clear how likely that is to happen.
This is very important. Most people would interpret “only transmitted by people showing symptoms” (or words to that effect) when they read it in a news outlet as meaning – well, as meaning exactly what it says. But post-symptomatic patients may still transmit the disease.
Is it possible that pre-symptomatic people can transmit the disease too? Personally I think it is possible even if it is generally unlikely. In a disease that kills over half of those who get it, “unlikely” is not comforting.