Okay, there's one new possible Ebola victim in NYC (though test not confirmed), and people freaking over fact he rode the subway while sick. So worth reviewing this from
recent NYT "Well" column:
It is extremely unlikely to spread through public transit, for several reasons.
Not all viruses build
up to infectious doses in all bodily fluids. For example, measles is
coughed out because it first invades cells at the back of the throat,
while H.I.V. is not. Norovirus is not a respiratory virus, but such
small doses are needed to infect a person that aerosolized vomitus is
thought to have sickened many cruise ship passengers. Normally, Ebola
does not at first make victims cough or sneeze, although someone who
also had the flu could, in theory, spray vomitus or blood. Once Ebola
invades the lungs, the body will cough to clear them. But passengers
that deathly ill are not likely to be on public transit.
According to the
recent W.H.O. statement, high levels of Ebola virus in saliva are rare
except in the sickest victims, and whole virus has never been found in
sweat. The fluids known to build up high viral loads are blood, feces
and vomit.
How much virus is
needed to cause illness is not exactly known. Viruses differ that way.
In any group that shares needles, hepatitis C will spread more readily
than H.I.V. because smaller doses infect.
One tantalizing possibility is that
very small doses of Ebola act as a vaccine.
Scientists working in Gabon have found that more than 30 percent of the
populations of some villages have Ebola antibodies, although they have
never been sick or in contact with anyone who was. They may have
swallowed some virus by eating infected bats or fruit contaminated with
bat saliva. (Alternatively, said W. Ian Lipkin, a virus expert, they may
have had an unknown virus that cross-reacted in antibody tests.)
No one has tested
Ebola transmission on subways. But no case of transmission to a human
from a dry surface has ever been confirmed. The C.D.C. has said there is
“no epidemiological evidence” for
transmission from hospital surfaces, including bed rails and door knobs – which are as close as a hospital room gets to having a subway pole and a bus handle. A
2007 study
cited by C.D.C. experts shows that swabs of 31 surfaces — including bed
frames, a spit bowl and a used stethoscope — in a very dangerous
environment, an active Ebola ward in Uganda, — did not have virus in a
single sample.
So how might Ebola be
passed on a subway? If someone ejected bloody mucus or vomitus onto a
subway pole, and the next passenger were to touch it while it was still
wet and then, for some unimaginable reason, were to put those wet
fingers into an eye or mouth instead of wiping them in disgust — then
yes, it could happen. Similarly, if an extremely ill passenger with high
viral saliva loads were to sneeze large, wet droplets directly into the
mouth or eyes of another passenger, the infection might be passed. But
the influenza route — sneeze to hand to pole to hand to eye — has never
been known to happen and is considered extremely unlikely.
Africa is full of
overcrowded public transport — buses, minivans and some trains. There
are no known instances of transmission in those environments.
On July
20, a dying Liberian-American flew to Nigeria and was vomiting on the
plane. All 200 people aboard were monitored; none fell ill.
And update tonight:
Can you get Ebola from a bowling ball?
A.
Although the surface of a shared bowling ball is a likely place to find
germs — and some people avoid bowling for this very reason — it is
extremely unlikely that Ebola could be passed that way.
There is no evidence that it has been passed, as colds or flu sometimes
are, by touching surfaces that someone else touched after sneezing into
their hand. Ebola is normally passed through contact with blood, vomit
or diarrhea.
If someone left blood,
vomit or feces on a bowling ball, and the next person to touch it did
not even notice, and then put his fingers into his eyes, nose or mouth,
it might be possible. But, the Ebola virus does not not normally build
up to high levels in saliva or mucus until very late in the disease —
several days after the initial fever sets in — and it is unlikely that
someone that ill would have just gone bowling. Also, the Ebola virus is
fragile and susceptible to drying out. It does not normally survive for
more than a few hours on a hard, dry surface.
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