H7N9 detected in four more China markets
As part of ongoing avian influenza surveillance, China's agriculture ministry yesterday reported H7N9 detections in four live-poultry markets in three provinces, including one—Ningxia—that hasn't reported any human cases.
Officials detected the viruses at different times in mid to late April and described the findings, which also occurred in Guangdong and Fujian provinces, yesterday in a report to the World Organization for Animal Health (OIE).
Ningxia province is in northwestern China, far from outbreak hot spots in the southern and eastern parts of the country. On Apr 25 authorities collected 80 chicken samples and 10 environmental samples from a live-bird market in Wuzhong, a city of about 1.3 million people in the central part of the province. One poultry sample tested positive for the virus.
In Fujian province, tests detected the virus at two live-poultry markets, one in Fuzhou and one in Xiaomen. Sampling involved chickens, ducks, and the environment. Two of 50 chicken samples were positive for the virus in Fuzhou, and one poultry sample was positive from the Xiaomen market.
In Guangdong province, tests on195 samples from a market in Huizhou yielded 1 positive sample.
May 7 OIE report
Epidemiologic report from Zhejiang finds short H7N9 incubation
An epidemiologic analysis of H7N9 infections during the outbreak's first wave in Zhejiang province, the hardest hit area during that time frame, found some unusual patterns. The report from Chinese researchers appeared today in BMC Infectious Diseases.
Their study included 46 lab-confirmed cases that occurred from Mar 31 to Sep 31, 2013. Unlike in other provinces, a larger percentage of patients (34.78%) were rural residents.
The team said it's not clear why Zhejiang province had more rural cases, but reasons could include accelerated integration between urban and rural areas in Zhejiang, which may have allowed live poultry to enter the areas after urban sales were temporarily suspended. They wrote that it's not clear if the rural residents were infected by backyard or market poultry.
Also, the median incubation period at 2 days was shorter than reported in other studies, which the researchers said could reflect multiple exposures to poultry and their environments, which were reported by eight of the patients.
Less than 5% of the case contacts had respiratory symptoms, and all of them tested negative for the virus. Researchers said all of the cases were sporadic, with no epidemiologic links between them.
May 8 BMC Infect Dis abstract
Meta-analysis highlights avian, swine strains causing human flu
A meta-analysis by leading European researchers published today in Eurosurveillance detailed more than 1,400 confirmed human cases of avian and swine influenza since 1959 and noted that, when H5N1 was taken out of the picture, the two types appear to be equally common. It should be noted, however, that the report does not include almost 200 of the most recent H7N9 cases.
The investigators included 89 of 6,955 potential articles in their review and focused exclusively on cases confirmed using virologic evidence. They detailed 1,419 distinct cases, of which 648 involved H5N1 avian flu. Among the others, 375 were associated with other avian flu subtypes and 396 with swine flu strains.
The leading non-H5N1 strain by far among the avian flu viruses was H7N9, accounting for 251 cases. The analysis, however, was limited to cases confirmed by the World Health Organization through Jan 31. The most recent H7N9 tally by FluTrackers, an infectious disease news board, is 435. The second leading avian flu strain was H7N7, accounting for 89 cases, followed by H9N2, at 15.
Swine strains were led by a large margin by variant H3N2, at 340 cases, followed by H1N1, at 47, and non-variant H3N2, at 7.
Not surprisingly, direct exposure to birds or pigs was the most likely source of infection for the cases that had available information. The researchers note that both avian and swine strains may be underrepresented in their report. Some avian strains cause only mild illness, and the symptoms of swine-origin flu often parallel those of seasonal flu.
The authors conclude, "To be prepared for a potentially emerging influenza virus of animal origin in humans, enhanced global surveillance in animal populations is therefore indicated to monitor evolution and circulation of viruses with yet unknown public health risks.
May 8 Eurosurveillance report
