At this point, there's no reason to believe that the emerging H7N9 strain of
bird flu that has sickened at least 24 people and killed seven in China is cause
for alarm, health officials in the United States say.
For one thing, no cases of human-to-human transmission of the virus have yet
been reported - a necessary precursor to a full-blown pandemic.
"This is very early in the course of identification of human cases," said Dr
John Midturi, assistant professor of internal medicine at the Texas A&M
Health Science Center College of Medicine, in Temple.
"We do see something similar every few years with avian [bird] flu," added
Richard Webby, a member of the department of infectious diseases at St Jude's
Children's Research Hospital in Memphis.
But this year's strain does seem a little different.
Sequence of the virus worrying
"What's making everyone a little bit more uneasy is that, looking at the
sequence of the virus, it appears to have some mutations we think may indicate
that the virus might have increased its ability to replicate in humans," Webby
But for now, there's no proof of that ability, he cautioned, and the genetic
sequence of the virus would still need to change for it to pass easily from
person to person.
The first human cases were not identified until March 31, according to
It's possible that the H7N9 virus is also found in some type of mammal, such
as swine, and public-health officials are working to identify possible
"We don't think that necessarily just this virus growing in [birds] would
cause some of these [genetic] changes," said Webby, who's also director of the
World Health Organization Collaborating Center for Studies on the Ecology of
Influenza Viruses in Lower Animals and Birds. "We can't say with any sort of
gusto that the last host of this virus was an avian host. Avian flu is a very
generic sort of term."
Chinese authorities are taking precautions against further spread of the
virus, suspending sales of live poultry in Shanghai and slaughtering poultry in
markets where the virus has been detected.
Treatable strain so far
The World Health Organization has announced that it was in talks with
the Chinese government about sending experts to help investigate the
The good news is that most of the human cases "have been associated with
poultry exposure, which is typical with most bird flu outbreaks," Midturi
However, the flu strain has also been found in live pigeons being sold as
poultry at a market in Shanghai. That has unnerved some experts since any
infection among wild pigeons would be tougher to control than among penned-in
The fatality rate from H7N9 also remains unclear. Although the death rate in
China seems high, with six deaths out of 16 confirmed cases, authorities don't
know at this point how many people have actually been infected.
"If hundreds or thousands of people contracted the virus with few or no
symptoms, the true fatality rate would be much lower," said Midturi, who is also
director of infectious disease at Scott & White Memorial Hospital in
The current outbreak is reminiscent of the outbreak of H5N1 avian flu in
2003, another bird flu that has killed about 370 people since then, according to
the World Health Organization. That outbreak raised fears about a pandemic that
There are also differences between the two viruses. Unlike H5N1, H7N9 doesn't
seem to cause illness in birds, making it harder to detect and track. But, it's
not unusual for flu viruses to not cause symptoms in their bird reservoirs, said
Dr Len Horovitz, a pulmonary specialist with Lenox Hill Hospital in New York
But he also added a bit of good news: H7N9 is treatable with currently
available antiviral medications.
According to The New York Times, the US Centers for Disease Control
and Prevention has started work on what's known as a "seed vaccine" for the
virus as a precaution. That vaccine will take at least a month to prepare.
And the Associated Press reported that Chinese health authorities
are also at work on a vaccine against H7N9.
"If there was human-to-human transmission, that would be worrisome," said
Horovitz. "[But] even then, we don't know how aggressive or fatal it would
Although two of the people who were sickened by the virus had had contact
with one another, right now it only "smells like the possibility" of
human-to-human transmission, Webby added.
"On the whole, it doesn't look like there's any strong evidence that this
thing is really running around rampant," he said.
There's more on H7N9 avian flu at the US
Centers for Disease Control and Prevention.
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