Study: evidence of subclinical H10N8 avian flu in animal workers in China
Some animal workers in southern China, home of the first H10N8 avian flu infections, may have had asymptomatic or subclinical infections with the strain even before the first human case was recognized in November 2013, so surveillance should continue in this population as well as in healthcare workers, say the authors of a study today in BMC Medicine.
The researchers, from Guangzhou, China, and Durham, N.C., retrospectively studied archived serum samples from 720 animal workers and 107 non–animal workers from May through August 2013 during a surveillance program for novel zoonotic flu in occupationally exposed individuals.
Samples were tested by hemagglutination inhibition (HI) assay; those with positive reactivity to H10N8 (defined as titer > 1:20) were further tested by microneutralization (MN) assay. Questionnaires given by the animal workers regarding risk factors for H10N8 were also evaluated.
Of the 827 samples, 21 (2.5%) tested positive, three with titers of 1:40. None of those who tested positive had flu symptoms during the 3 months before sampling was done. Of the three people with the higher titers, two had MN antibody titers of 1:40, evidence of possible previous H10N8 infection, and one had a titer of 1:80, indicative of a probable previous infection. All three were animal workers.
H10N8 virus was first identified in a duck in Guangdong province during 2012; the authors say the virus infected dogs in the area as well. They point out that the Guangdong province has been a hotbed of novel influenza virus generation, including the H7N9 strain that is the source of an ongoing outbreak that began in 2013 and has caused more than 450 cases.
Oct 27 BMC Med abstract
Five strains of H5 avian flu reported across China
Reports of outbreaks in China involving five different highly pathogenic H5 avian influenza strains were filed with the World Organization for Animal Health (OIE) recently.
Two of the strains—H5N8 and H5N3—have not been reported by China to the OIE before. Two outbreaks of the former were reported in September, each involving one bird (a duck and an unspecified bird) sampled during a national surveillance plan. One was at a slaughterhouse and the other in a wetland area; both were in Liaoning province in the northeast.
H5N3 occurred in a duck at a live-bird market in China’s south central Hunan province. The bird’s infection was also discovered during surveillance.
Eight outbreaks of H5N2 on farms, at bird markets, and in wetland areas were reported from Sep 12 through Oct 24. The total susceptible birds numbered 6,254, of which 6,253 were destroyed (1 bird was discovered during surveillance). Geographic areas affected included the following provinces: Hubei in the east central region (three outbreaks), Heilongjiang and Liaoning in the northeast, Ningxia and Liaoning in the northwest, Guangxi in the south central region, and Tibet.
Twenty-four H5N6 avian flu outbreaks among ducks, geese, and chickens at markets and farms were reported to the OIE in September, all but one involving just one or two birds during sampling done as part of a national surveillance plan. The larger outbreak was on a farm in Heilongjiang province. Two birds in a flock of 1,421 were infected, and all birds were destroyed.
H5N1 avian flu was the cause in 16 outbreaks, all of them involving 1 or 2 ducks, geese, or chickens, again occurring at markets and discovered as part of national surveillance.