Avian Flu Scan for Sep 07, 2017

Lab-created H5N8-H5N1 virus
;
H7N9 fifth-wave features
;
Bird outbreaks in Taiwan, Italy

H5N8-H5N1 avian flu combo virus shows increased virulence in mice

In the latest gain-of-function (GOF) study, South Korean researchers have substituted genes from H5N1 avian influenza onto an H5N8 avian flu virus and found that it caused greater pathogenicity and up to a 1,000-fold greater virulence in mice.

Writing in the journal Virulence, the investigators did not alter the virus by serial passaging it in lab animals, as has often been the case with GOF studies. Instead, they generated reassortant viruses in the lab using an H5N8 backbone virus from South Korea in 2014 and then substituting individual genes from an H5N1 virus that was obtained in South Korea in 2006 so they could understand the contribution of each individual gene to virulence in mammals.

They found that substituting the PB2 gene segment or the NA gene segment from the H5N1 virus resulted in significantly enhanced pathogenicity in lab mice compared with the parental H5N8 virus. Notably, substituting the PB2 gene segment resulted in a 1,000-fold increase in virulence in mice compared with the parental virus. The reassortant virus with that substitution also induced the highest virus titers in lungs at all test intervals and the greatest inflammatory cytokine response among all viruses tested.

The authors conclude, "Our study demonstrates that a single gene substitution from other avian influenza viruses can alter the pathogenicity of recent H5N8 viruses, and therefore emphasizes the need for intensive monitoring of reassortment events among co-circulating avian and mammalian viruses."

South Korea had extensive H5N8 outbreaks in poultry over the winter and into the spring of this year.

GOF studies enhance the pathogenicity, transmissibility, or host range of a pathogen to learn more about it. They have triggered "dual-use" concerns—worries that research meant for beneficial purposes could be used to create bioterror threats or for other ill purposes.
Sep 5 Virulence abstract

 

Wrap-up of China's fifth H7N9 waves highlights dominance of new lineage

The number of towns, provinces, and regions that reported human cases in China's unprecedented fifth wave of H7N9 avian influenza activity, which began in October 2016, is higher than the previous four waves combined, researchers from the US Centers for Disease Control and Prevention and their collaborators in China reported today in the latest edition of Morbidity and Mortality Weekly Report (MMWR).

In their wrap-up of the latest epidemiologic and genetic sequencing information, the group said 759 illnesses were reported in the fifth wave, 281 of them fatal, and that among several new developments over the past months, the newly emerged Yangtze River Delta low pathogenic lineage accounted for most of the activity and scores as having the highest potential pandemic risk (moderate to high) on the CDC's Influenza Risk Assessment Tool. In February, World Health Organization (WHO) flu vaccine advisors recommended new candidate vaccine viruses for the Yangtze River Delta lineage, for which current H7N9 candidate vaccine viruses show limited protection.

Other notable features of the fifth wave were the emergence of the highly pathogenic strain in poultry, which was found in 27 of 759 cases and was most often seen in those from rural areas, people with early hospital admission, and in those who had been exposed to sick or dead poultry, according to the report.

Despite the wider geographic spread, the patterns of spread from poultry to humans and from human to humans haven't changed much, the group said. Fourteen clusters of two or three people were reported to the WHO in the fifth wave, compared to an average of nine in each of the earlier waves.  Transmission from poultry is rare and the virus doesn't pass easily among people, but when infections do occur, they are linked to severe and fatal infections, requiring close vigilance, they added.
Sep 8 MMWR report

 

More avian flu outbreaks reported in Taiwan, Italy

In separate notifications over the last 2 days, the World Organization for Animal Health (OIE) detailed more events regarding ongoing highly pathogenic avian influenza activity, one in Taiwan and the other in Italy.

In Taiwan, another H5N2 outbreak was detected, this time at a slaughterhouse in Taipei City. The virus was found after authorities saw signs of disease in carcasses of native chickens on Aug 18 during the postmortem inspection, which prompted testing. Ten carcasses were destroyed, and a trace back investigation is underway to find the farm that sourced the poultry. Taiwan has been battling several outbreaks involving H5N2, as well as other strains, since early 2015.

Elsewhere, Italy reported another H5N8 outbreak at a turkey farm in the Lombardy region in the north central part of the country. The event began on Sep 2, killing 45 of 23,193 susceptible birds. The rest of the flock is slated for culling. H5N8 has surfaced in a few European countries over the warmer summer months, but Italy has been hardest hit, especially commercial turkey producers.
Sep 6 OIE report on H5N2 in Taiwan
Sep 7 OIE report on H5N8 in Italy

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