Chinese woman's illness lifts H7N9 case total to 131

May 7, 2013 (CIDRAP News) – A 79-year-old woman from China's Jiangxi province has been hospitalized with H7N9 avian flu, moving the outbreak total to 131 cases, including 31 deaths.

Hong Kong's Centre for Health Protection (CHP), which cites China's National Health and Family Planning Commission, said in a statement today that the woman is in stable condition and that none of her 11 close contacts has shown symptoms so far.

A translated report from the Jiangxi provincial health department posted on the FluTrackers infectious disease message board said the woman is a farmer who had free-range poultry such as chickens and ducks at her residence.

The World Health Organization (WHO) posted an update on the H7N9 outbreak today, and though it didn't include the new case from Jiangxi province, it had a few more details about two other recently confirmed case-patients from Fujian province. One is a 69-year-man who got sick on Apr 29, and the other is a 9-year-old boy who became ill on Apr 26.

According to earlier CHP reports, the man is hospitalized and the boy has been released.

The WHO said contacts of confirmed cases are being closely monitored, but so far there is no evidence of sustained human-to-human transmission.

In other developments, a research group from China yesterday published a genetic sequence analysis of an H7N9 isolate collected from one of the first four patients, a 38-year-old man from Hangzhou in Zhejiang province who got sick on Mar 7 and died on Mar 27. The team published its findings in a letter in an early online edition of Clinical Infectious Diseases (CID).

The virus, influenza A/Hangzhou 1/2013, was also included in other recent genetic analyses in the Apr 11 issue of Eurosurveillance and the May 1 issue of The Lancet.

The authors of the CID study reported similar findings, that the H7N9 virus had markers necessary for human receptor binding, which they said could be responsible for spillover infections from birds to humans. Their analysis of the hemagglutinin (HA) and neuraminidase (NA) genes of H7N9 were also similar.

Their homology analysis found that the HA gene was similar to that of an H7N3 virus isolated in a duck from Zhejiang in 2011 and that the NA gene was similar to an H11N9 viruses obtained from a Czech Republic mallard in 2010 and a Baikal teal duck from Hongze Lake in China's Jiangsu province in 2005.

The group's phylogenetic analysis found similar findings, and the researchers suggested that the new H7N9 virus was reassorted from the Zhejiang duck H7N3 virus and the Baikal teal H11N9 virus.

When they compared the HA and NA sequences from the H7N9 virus with other H7 and N9 sequences in flu databases, they found that both the H7N9 HA and NA genes seemed to show independent evolution, which they said militates against their involvement in the recombination event.

"Reassortment from mixed infections between influenza subtypes was more likely for this new H7N9 subtype development," they wrote.

See also:

May 7 CHP statement

May 7 FluTrackers thread

May 7 WHO update

May 6 CID letter landing page

Apr 11 Eurosurveillance study

May 1 Lancet abstract

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