Cases of the new H7N9 avian influenza in China are surging alarmingly, flu experts warned this week.
There are now about 300 confirmed cases, with more appearing every day. Roughly a quarter of the victims have died.
The
first human cases were reported only last March. By contrast, the H5N1
influenza virus, another lethal strain that jumped from birds to people,
first appeared in 2003 and took almost five years to reach the 300-case
mark.
“H7N9 is blowing right by H5N1,” said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. “I’m really worried about that.”
At
the same time, an even newer avian flu in China has killed its first
human victim. That strain, known as H10N8, has been confirmed in only
two people — a 73-year-old woman who died in December but whose
infection was confirmed later, and a 55-year-old woman from the same
province hospitalized in January. Both had contact with live poultry.
(Influenzas
are described by the shapes of two protuberances on their surfaces: the
hemagglutinin “spike,” or “H,” that attaches to cells, and the
neuraminidase “helicopter,” or “N,” that chops off receptors, allowing
new viruses to escape. There are 18 known types of H and 11 of N.)
While
the newer influenza virus is worrisome, a mere two cases is “a far, far
cry” from the risk posed by H7N9, said Ruben Donis, chief of
preparedness for the flu division of the Centers for Disease Control and
Prevention. He noted that the H7N9 virus had infected people in 10
Chinese provinces and was close to the borders of Vietnam, Cambodia and
other poor Southeast Asian nations less adept than China at flu
surveillance.
Birds
appear to be spreading the H7N9 virus more through their breath than
through feces, the normal infection route, Dr. Osterholm said, which
means that fecal-sample testing in live markets may miss cases.
Monitoring
the spread of the H7N9 and H10N8 viruses is difficult because neither
makes chickens sick. Poultry farmers resist testing because a positive
test forces them to destroy flocks that appear healthy. By contrast, the
H5N1 virus rapidly kills flocks, so farmers want it extinguished.
Although
human-to-human transmission of the H7N9 virus has not been confirmed,
there have been clusters of two or three cases within families.
Because some relatives were reported to have developed symptoms days later than others, Henry L. Niman, a flu watcher in Pittsburgh who monitors news reports, said the most likely explanation was that they infected each other.
Dr. Osterholm disagreed, saying family members could have been exposed to the same birds but fallen ill on different days. http://www.nytimes.com/2014/02/05/health/cases-of-new-deadly-bird-flu-surge-in-china-experts-say.html?_r=0
