A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org
In this update:
[1] Now 96 cases and 18 deaths
[2] Age and gender profile
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[1] Now 96 cases and 18 deaths
Date: Sat 20 Apr 2013
Source: English new, Xinhua report [edited]
http://news.xinhuanet.com/english/health/2013-04/20/c_132326162.htm
During the 24-hour period ending at 4 p.m. on Sat 20 Apr 2013, China confirmed 5 new cases of human H7N9 avian influenza, including one in Shanghai, one in Jiangsu and 2 in Zhejiang. The National Health and Family Planning Commission said in its daily update on H7N9 cases that a total of 96 H7N9 cases have been reported in China, including 18 that have ended in death. Of the total, 9 H7N9 patients have been discharged from hospitals after receiving treatment, and the other 69 patients are being treated in designated hospitals, according to the commission.
A total of 33 cases, including 11 that have ended in death, have been reported in Shanghai. 22 cases, including 2 deaths, have been reported in Jiangsu Province, and 33 cases, including 2 deaths, in Zhejiang Province. Anhui Province has reported 2 cases, with one ending in death. Beijing has reported one case, and 2 have been reported in Henan Province.
China officially confirmed the occurrence of humans infected with the H7N9 virus late last month [March 2013]. According to the commission, China's confirmed H7N9 cases are isolated, and there has been no sign of human-to-human transmission.
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Communicated by:
Ryan McGinnis
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[2] Age and gender profile
Date: Fri 19 Apr 2013
Source: CIDRAP News [edited]
http://www.cidrap.umn.edu/cidrap/content/influenza/h7n9/news/apr1913ageh7.html
One of the odd mysteries posed by the H7N9 influenza virus emerging in China is why most of the patients are on the older side, a fact that stands in sharp contrast to the pattern seen with that other deadly crossover avian virus, H5N1. An analysis by Nicholas Kelley, PhD, at the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), shows that the median age of H7N9 case-patients thus far is 61.5 years, with a range of 2 to 89 years. For comparison, Kelley examined the ages of the 45 H5N1 case-patients in China over the past 10 years and found a median age of only 27. And when he looked only at H5N1 cases in the same provinces where H7N9 cases have turned up, the median age was even younger: 24. The European Centre for Disease Prevention and Control (ECDC), in an epidemiological update released today [19 Apr 2013], but based on cases as of yesterday, put the median age of H7N9 patients even higher: 64, with a range of 4 to 89.
A related puzzle is the gender balance, or rather imbalance, among H7N9 cases. The ECDC report says just 25 of 82 patients with available information have been female. For H5N1, the gender balance has been much more even. Looking at H5N1 cases in the same provinces as the H7N9 cases, Kelley found that 11 were female and 9 were male.
So far, authorities on influenza generally seem stumped by these differences, much as they are stumped on exactly how the virus is getting into humans. The suspected source is poultry, but Chinese authorities reported this week that only 39 of about 48 000 samples from more than 1000 poultry markets, farms, and other sites were found to contain the virus. Further, they said about 40 percent of H7N9 patients had no clear history of exposure to poultry.
Timothy Uyeki, MD, MPH, a flu expert at the US Centers for Disease Control and Prevention, said this week that any suggested reasons for the age distribution would be only speculation, because there's just not enough information to offer any answers. Likewise, experts at the ECDC didn't have any answers. "They said we just don't have information at this point, so prefer not to speculate," said Romit Jain, an ECDC communication officer.
Yuelong Shu, PhD, director of the Chinese National Influenza Center in Beijing, suggested this week that older people may have more exposure to H7N9 because of greater contact with poultry, compared with younger people. "Usually the retired older people take care of the family food in China," and thus are more likely to visit poultry markets, he commented by e-mail. "But the exact reason [for the age distribution], we really don't know."
Michael T. Osterholm, PhD, MPH, director of CIDRAP, ticked off several variables that might be considered in the search for an explanation of the different age and gender distributions but said none of them offers an answer at this point. For example, is there a difference between H5N1 and H7N9 in how cases are detected, such that younger people infected with H7N9 would tend to be missed? "If you look at H5N1 cases just from the same provinces where we see H7N9 cases, it would be hard to hypothesize what the major differences would be in detection and treatment of cases," Osterholm said.
Another possibility, he said, would be age-related differences in underlying conditions between H5N1 and H7N9 case-patients. "Again, if you look at the same provinces, it's unclear what that would be," he said.
Underlying immunologic factors in older people who are exposed to H7N9 might be another thing to consider. "That could be the case if the illnesses [with H5N1 and H7N9] were very different," Osterholm said. "But we don't have any evidence of that here. The descriptions of the illness are very similar to what we see with H5N1." For example, he added that the median time from onset to death in fatal H7N9 cases is 13 days, very similar to the time in H5N1 cases.
As for exposure to poultry at live-bird markets or elsewhere, Osterholm said that that risk factor clearly operates with H5N1 so doesn't explain the different demographics of the 2 viruses. Another possibility might be some inherent difference between the 2 viruses, he said. But he ruled that out too: "It's never just the virus. It's the virus-human relationship."
The age and gender patterns are just 2 of multiple H7N9 mysteries waiting to be cleared up. Another is why more than 80 [now 96] H7N9 cases have popped up in just a few weeks in China versus just 45 H5N1 cases in the country in about 10 years. Still another puzzle is why the virus seems to cause little or no sickness in birds but makes humans seriously ill. "We don't know what we're dealing with here, because this is the 1st time we've seen a virus causing serious illness in humans but having low pathogenicity in birds," Osterholm said.
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Communicated by:
Ryan McGinnis
[Maybe the prefix "Avian" is unjustified? - Mod.CP
