Flu Scan for Dec 24, 2014

Asymptomatic H7N9 infections
Avian flu in British Columbia
Increased global flu

Signs of subclinical infection found in 10% of H7N9 patient contacts

Chinese researchers who tested 225 close contacts of H7N9 influenza patients found that about 10% of them carried antibodies suggesting they had been infected with the virus without getting sick, according to a letter yesterday in Emerging infectious Diseases.

The report notes that human-to-human transmission of H7N9 is not common but that reports suggest it has probably occurred in family and household clusters and between a doctor and a patient.

The researchers report that 10 H7N9 cases occurred in the city of Wuxi in Jiangu province from late March 2013 to mid-May 2014. They enrolled 225 contacts of 7 of those patients in the study, including 30 family members and 177 healthcare workers.

Hemagglutination inhibition (HI) assays were used to test for antibodies against H7N9, H5N1, H9N2, and seasonal flu viruses H1N1 and H3N2. The tests were conducted between 2 and 4 weeks after the participants' first exposure to an H7N9 patient. All contacts denied having any flu-like respiratory symptoms during the 28 days of follow-up and also denied any recent exposure to poultry or pigs or their environments, the report says.

The results showed that 22 (9.8%) contacts had elevated HI antibody titers (at least 1:40) against H7N9; titers were 1:40 for 17 contacts and 1:80 for 5 contacts. In addition, 108 contacts had HI titers of at least 1:80 against seasonal H3N2 virus, but none had titers greater than 1:80 against H5N1 and H9N2 viruses.

The authors write that one limitation of their study is that they did not collect serum samples from all contacts of infected persons or from controls, and therefore they couldn't assess the possibility of false-positive results or asymptomatic infections. Nonetheless, they say their findings "offer evidence that human-to-human transmission of H7N9 virus may occur among contacts of infected persons."
Dec 23 Emerg Infect Dis letter


Backyard flock in British Columbia hit with avian flu

The Canadian Food Inspection Agency said that 85 ducks, chickens, geese, and turkeys in a backyard flock in Aldergrove in British Columbia's Fraser Valley have contracted avian flu, CBC News reported yesterday.

This is the first backyard flock affected this year in that region. Officials have previously confirmed H5N2 avian flu on 11 commercial poultry farms, the story said. Nearly 250,000 chickens and turkeys have been affected on those farms. Aldergrove is just west of Abbotsford, the site of several of the affected farms.

Officials have not yet identified the source of the outbreak. So far no wild birds in Canada have tested positive for H5N2, but a wild duck across the border in Washington state tested positive for that strain last week.

In 2004 H7N3 avian flu struck dozens of farms in the Fraser Valley region, affecting about 17 million birds.
Dec 23 CBC News report


Global flu activity rises

Influenza activity is picking up across the Northern Hemisphere, with the H3N2 strain dominating by a large margin, the World Health Organization (WHO) said yesterday in its weekly update.

H3N2 is dominant both in North America, where flu activity has passed seasonal threshold levels, and in Europe, where flu activity increased but remained at low levels. WHO data are complete through Dec 13.

Flu circulation also increased in East Asia, with H3N2 dominating, and North Africa, with influenza B virus predominating.

In contrast, flu activity was low or decreasing in eastern and western Africa, tropical Asia, and tropical areas of the Americas. Exceptions were Tanzania, which reported increased H3N2 detections, and Costa Rica and Cuba.

Flu is at interseasonal levels in the Southern Hemisphere, the agency reported.

According to FluNet reporting, 94% of specimens tested were influenza A. Of the 6,134 "A" strains subtyped, 98% were H3N2, with the rest subtyped as 2009 H1N1. All but 1 of 135 influenza B isolates were of the Yamagata lineage.
Dec 23 WHO update

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