The mortality rate in the H7N9 avian influenza outbreak has reached 20%, according to the latest figures from the World Health Organization.
With 128 laboratory-confirmed cases of human infection as of May 2, there have also been 26 deaths, or 20.3%. At the same time, 26 people have recovered from the novel illness, according to the China Center for Disease Control and Prevention.
"The cases are going up daily -- about 20% have died, 20% have recovered and the rest are still sick," commented John McCauley, PhD, director of the WHO Collaborating Centre for Influenza in the United Kingdom.
"The WHO considers this a serious threat," McCauley told the Guardian newspaper. "We're on an alert and we're developing diagnostics and vaccines specifically against the virus."
While the mortality is high, it is, so far, lower than that seen in cases of infection with the highly pathogenic H5N1 avian flu, which approaches 50%. As of April 26, the WHO is reporting a total of 628 laboratory-confirmed cases of H5N1 in humans, with 374 deaths.
The highly pathogenic H5N1 flu causes severe illness in both birds and people, but is easily transmitted only among fowl.
In contrast, the H7N9 virus appears to cause disease -- so far -- only in people; infected birds do not show signs of illness, making the virus difficult to track.
Fortunately, there is little evidence so far of human-to-human transmission of the virus, but exactly how it is spreading remains unclear, although suspicion centers on domestic fowl and perhaps wild birds. But in many cases, there is no obvious link between patients and birds.
Earlier this week, researchers reported that genetic analysis of flu isolates from several patients as well as those taken from domestic and wild birds suggests the novel virus derives from at least four sources.
Among the possible sources are domestic chickens, which are often transported from place to place and could therefore be a vector for the virus, the researchers reported.
The virus emerged in China in late winter, was identified by surveillance for unexplained pneumonia in late March, and the first cases were reported to the WHO March 31.
The news of that outbreak came as attention was focused on another novel pathogen. A coronavirus, dubbed hCoV-EMC, that had emerged from the Middle East was pushed off the front pages by the H7N9 flu.
But May 2, the WHO said it had received reports of seven new laboratory confirmed cases of the novel coronavirus, of which five patients had died and two remain in critical condition.
It was the first report of new cases since March 26 – just before the news broke of the H7N9 outbreak.
Since the coronavirus emerged last September, there have been a total of 24 laboratory confirmed cases around the world, and 16 patients have died.