Ebola Virus: A Grim, African Reality, by David Quammen
Source: http://www.nytimes.com/2014/04/10/opinion/ebola-virus-a-grim-african-reality.html?_r=0
(
There’s
nothing like an outbreak of Ebola virus disease to bring a small,
struggling African nation to international notice. One week we couldn’t
place it on a map; the next week, after Ebola virus disease strikes, we
know the body count and the name of the capital and whether its airport
has closed.
This sad distinction now attaches to Guinea,
a country of 11.5 million, in which the latest of Africa’s viral
tribulations was reported by the World Health Organization, upon
notification from Guinea’s Ministry of Health, on March 23. As of
Tuesday the toll was 157 confirmed or suspected Ebola cases, including
101 deaths. That’s a case fatality rate of 64 percent, somewhat lower
than the worst of previous outbreaks but high enough to remind us that
Ebola is more inimical to humans than perhaps any known virus on Earth,
except rabies and HIV-1. And it does its damage much faster than either.
Among
neighbors just across Guinea’s southeastern border, Liberia has
confirmed several Ebola cases of its own, in people who recently
traveled from Guinea, and Sierra Leone is watching very carefully. No
one wants this thing to spread.
The
Guinea outbreak has also raised one puzzling new question about Ebola:
What is this particular species of virus, known technically as Zaire
ebolavirus, doing way over in West Africa, so far from the Central
African forests in which all its previous outbreaks have occurred?
Viruses don’t travel, except in other living creatures. It seems to have
hitched a lift, across Nigeria and Ghana and Ivory Coast and other
intervening nations, within something or someone. Maybe it was carried
by a bat.
Scientists
have identified a total of five species of ebolavirus, four native to
Africa and one to the Philippines. They are all zoonoses, meaning animal
infections transmissible to humans. They reside quietly in some species
of wildlife, this or that forest creature, from which they spill over
occasionally to cause mayhem and death in people. Ebola virus can only
pass from person to person by direct contact with bodily fluids, and
therefore an outbreak is stoppable by simple isolation and “barrier
nursing,” or the careful handling of patients and corpses, once enough
medical gloves, gowns, goggles, rubber boots, body bags and knowledge
have reached the scene.
Although
the outbreak is eventually halted, the virus isn’t gone. It hides in
the forest within some hospitable animal, its reservoir host. The
identity of the reservoir host (or hosts) for Ebola virus is unknown,
but three species of fruit bat are suspected. One of those species, the
hammer-headed fruit bat, lives in forests from the Congo basin as far
west as southeastern Guinea and is sizable enough to be attractive as
human food.
In
Guinea, the index patient (the first case) has not even been
identified, though the preponderance of cases in Guéckédou, a city near
the southeastern border, suggests that the outbreak may have begun down
there. Without knowing the index patient, investigators can’t know how
the fateful spillover happened. Did someone eat a bat? Did someone
scavenge another dead chimp, one that had shared fruit with a bat?
That
sort of research will have to come later, I was told recently by Dr.
Stuart Nichol, of the Centers for Disease Control and Prevention. Dr.
Nichol, himself a veteran of many outbreak responses, is chief of the
C.D.C.’s Viral Special Pathogens Branch, a portfolio containing all the
world’s nastiest viruses. Some of his people are presently in Guinea.
For now, Dr. Nichol said, the focus is on human health: identifying
cases, getting them isolated, giving them supportive care (there are no
real treatments for Ebola virus disease), tracing contacts, breaking the
chains of transmission.
The
original Zaire species of ebolavirus was the first recognized back in
1976, when it emerged at a place called Yambuku in the northern
boondocks of what then was Zaire, now the Democratic Republic of Congo.
Of the 318 people infected, 280 (88 percent) died. A later outbreak in
northeastern Gabon, in 1996, began with a chimpanzee carcass, scavenged
from the forest by a group of boys on a hunting foray and devoured
communally back at their village. (Chimps cannot be the reservoir host
of Ebola because they too die from it, as this one evidently had.)
Thirty-one human cases, 21 deaths. The Zaire virus has also struck three
times in the Republic of Congo just across the river, killing dozens of
people each time.
In
all, since 1976, more than two dozen outbreaks of the various
ebolaviruses have accounted for just over 1,640 reported deaths. So it’s
a terrible thing, Ebola virus disease, but relatively rare.
没有评论:
发表评论