China has reported three new H7N9 influenza cases over the past 4 days from Fujian, Jiangsu, and Hunan provinces, continuing a slow trickle of infections, as Chinese researchers teased out connections between positive market findings and human infections.
Two of the cases were announced on Mar 29. They include a 72-year-old man from Fujian province who is listed in severe condition at a Fuzhou hospital and a 35-year-old man from Jiangsu province who is hospitalized in Wuxi in critical condition, according to provincial health ministry statements translated and posted by FluTrackers, an infectious disease news message board.
The third case was reported today from Hunan province, in a 65-year-old man who is hospitalized in the city of Shaoyang, according to health department statement translated and posted by FluTrackers.
The trio of new infections boosts the outbreak total to 405 cases, based on a running human case list kept by FluTrackers. The unofficial number of deaths remains at 122. So far 269 illnesses have been reported in the send wave of H7N9 infections that began in October, compared with 136 in the first wave last spring.
Study probes infection-market links
In other developments, a study by Chinese researchers that explored the connection between sick patients and poultry markets found that contaminated markets appear to be driving the outbreak, though the levels of environmental samples that tested positive didn't correlate closely with the levels of human infections.
The team, which included researchers from the Center for Disease Control and Prevention in the Zhejiang province capital of Hangzhou, published its findings today in BMC Infectious Diseases.
The investigators focused on exposures and epidemiologic patterns in human cases in Hangzhou that were reported early in the first wave of the outbreak, from Apr 1 through May 1 of 2013. Their analysis included 30 patients, who ranged in age from 38 to 86. The median age was 62. Among the patients, 23 were men and 7 were women.
Medical observation of 666 close contacts found no other infections. However, tests on 314 environmental samples collected from markets where the patients or their families shopped found a positive H7N9 detection rate of 29.0%. Positive findings were found in eight of Hangzhou's districts.
The team found a statistically significant different between the case-linked locations and the non-case locations. Also, the group didn't find any epidemiologic links between any of the patients.
They noted that most of the infected patients were retired people age 60 or older, mostly men who visited live-poultry markets daily to buy food ingredients, including live poultry. In China, live poultry is often slaughtered at the point of purchase to ensure freshness. Patients were likely repeatedly exposed to contaminated markets for significant periods and may have had contact with live birds and freshly slaughtered poultry without proper precautions.
Frequent exposure to the poultry markets can make it difficult to calculate incubation periods, the authors observed. However, more definitive exposures to poultry and their environments were available for 12 of the patients, including 9 who had single visits. The researchers estimated the incubation period to be from 1 to 14 days, with a median of 7 days, which they wrote is longer than for the H5N1 virus.
They found that, in environmental testing, the H7N9 positive rate was highest in a district where only two cases were confirmed and that other districts with lower rates were linked to a higher number of human cases.
H7N9 modification in lung cells
In other research developments, French researchers noted a pattern in H7N9-infected human lung cells similar to a few other influenza A viruses, including the 2009 H1N1 virus. The group reported its findings on Mar 28 in Virology.
They found that H7N9 infection in the cells was linked to the formation of many M1-associated striated tubular structures within the nucleus and cytoplasm, which have been seen before in only a limited number of influenza A viruses. They wrote that the role of the structures in viral replication and pathogenesis should be explored further.
See also:
Mar 29 FluTrackers thread
Mar 31 FluTrackers thread
FluTrackers human H7N9 case list
Mar 31 BMC Infect Dis abstract
Mar 28 Virology abstract
