Flu Scan for Aug 12, 2016

Two more H3N2v infections
Chinese H7N9 cases
H5N3 hits France again
Fall bird migrations and H5N1

CDC reports two new swine-linked H3N2v cases in Ohio

Two new variant H3N2 (H3N2v) influenza cases have been reported in Ohio, both of them in people who had contact with pigs at agricultural fairs, the Centers for Disease Control and Prevention (CDC) said today in its weekly flu update. The report also notes two H3N2v cases that were reported in Michigan a week ago.

"Separate swine exposure events at fairs in each state are associated with infection and there is no indication that the cases in different states are related," the CDC said. It added that H3N2 viruses were found in at least one swine respiratory sample collected at each of the fairs involved.

Public health and agriculture officials are looking for further cases in humans and swine, but no increases in flu-like illness in the communities have been reported, the CDC said.

The CDC gave no other details on the Ohio cases, but the Associated Press (AP) reported that they involved two children who attended the Clark County Fair in west-central Ohio in late July. The Michigan cases involved swine exhibitors at the Muskegon County Fair, Michigan officials said in reporting the cases.

No information on the condition of the H3N2v patients was released. Most cases in the past have been mild.

H3N2v was first found in humans in 2011, and the following summer brought more than 300 cases in the United States, most of them linked to swine exposure. Since then, only sporadic H3N2v cases have been detected. The virus is a swine H3N2 that contains the matrix (M) gene of the 2009 H1N1 virus, which scientists say could enhance its transmissibility.
Aug 12 CDC FluView update
Aug 12 AP story
Aug 8 CIDRAP News item on Michigan cases


Five new H7N9 cases in China include cluster

China announced five more H7N9 avian influenza cases, three of them linked to each other and one of them fatal, according to a report today from Hong Kong's Centre for Health Protection (CHP), which cites the mainland's National Health and Family Planning Commission.

The latest cases span three different provinces, and most involved exposure to poultry or their environments. Two patients are from Fujian province: a 79-year-old man who got sick after visiting a market and died on Jul 10 and a 78-year-old man who had been exposed to poultry and is hospitalized in serious condition.

The third patient is a 35-year-old man from Beijing who got sick after he was exposed to poultry in Jiangxi province. The man is hospitalized in serious condition.

The fourth and fifth case-patients, from Hebei province, are a 13-year-old girl and a 68-year-old woman who live together and are listed in stable condition. The girl had accompanied the Beijing man back to Jiangxi province, the CHP said.

H7N9 has become enzootic in mainland poultry, with China's agriculture ministry reporting positive poultry market samples from 10 of China's provinces between January 2015 and May 2016, according to the CHP.

The new cases boost the global H7N9 total to 807 cases, according to a list maintained by FluTrackers, an infectious disease news message board.
Aug 12 CHP statement
FluTrackers H7N9 case list


Another French poultry farm hit by low-path H5N3 virus

Another poultry farm in southwestern France has been infected by a low-pathogenic H5N3 avian flu virus, French officials said in a report posted yesterday by the World Organization for Animal Health (OIE).

During regular surveillance, the virus was found on a farm housing 5,000 ducks in Pyrenees-Atlantiques department, the report said. None of the birds were sick, but all were destroyed to prevent any further spread of the virus.

The report came on the heels of one posted earlier yesterday that detailed H5N3 outbreaks on duck and goose farms in Tarn and Gers departments, also in France's southwest.

The number of avian flu outbreak detections in France since late 2015 has reached 84. The outbreaks have featured five new avian flu viruses of European origin, of which three are highly pathogenic.
Aug 11 OIE report
Aug 11 CIDRAP News item on earlier outbreaks


Autumn migrations said to be key in spread of H5N1 by wild birds

Southward autumn migrations of wild birds appear to be much more important in spreading the highly pathogenic H5N1 avian influenza virus than are northward spring migrations, according to an analysis by scientists from China and the Netherlands.

The scientists, who published their results Aug 10 in Scientific Reports, examined the directions of H5N1 transmission and the concentration of H5N1 clades and compared those findings with the directions of seasonal waterfowl migrations along major flyways.

Out of 22 H5N1 transmission directions, they found, 18 were southward and involved relatively high concentrations. Also, the differences between the directions of H5N1 transmission and waterfowl migrations were significantly smaller for autumn than for spring migrations.

"The four northward transmission directions were found along Asian flyways, where the initial epicenter of the virus was located," the authors wrote. "We suggest waterfowl first picked up the virus from East Asia, then brought it to the north via spring migration, and then spread it to other parts of [the] world mainly by autumn migration."

The scientists suggest a few possible reasons for the close links between autumn migrations and H5N1 transmission. One is that the numbers of migrating birds are greater in the fall, because they include young birds born in the preceding breeding season. Also, the increased number of young birds in the fall leads to a higher infection rate, since juveniles are more vulnerable to the virus.

The findings suggest it would be wise to "strengthen the surveillance and control [of H5N1] at waterfowl breeding sites, stopover sites during autumn migration, and wintering sites," the authors say. In addition, because Siberia is "the major hub" in global H5N1 transmission and the starting point for several flyways, they recommend investigation of disease transmission at the northern breeding sites.
Aug 10 Sci Rep article

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