H7N9 avian flu sickens two in China
China is reporting two new H7N9 avian influenza infections, the first since July. The new cases potentially mark the start of the fifth wave of infections.
One of the patients is a 77-year-old woman who works as a farmer near the Jiangsu province city of Huzhou who bought poultry from a live market before she became ill, according to a statement today from Hong Kong's Centre for Health Protection (CHP). She is hospitalized in serious condition.
The other case involves an 89-year-old man from the city of Suzhou in Zhejiang province who is also listed in serious condition.
A CHP spokesman said in the statement, "As winter approaches, based on the seasonal pattern of avian influenza viruses, their activity in the Mainland is expected to increase. The public should avoid contact with poultry, birds and their droppings and should not visit live poultry markets and farms to prevent avian influenza."
Since the novel virus emerged in 2013, 809 cases have been reported, most of them from China, according to a case list kept by FluTrackers, an infectious disease news message board.
Nov 11 CHP statement
FluTrackers global H7N9 case list
Childhood exposures to influenza determine future immunity
For the last decade, scientists have wondered why novel influenza A viruses have attacked certain age groups at higher rates. Now, a new study published in Science explains that the first strain of influenza a young child is exposed to determines their future susceptibility to different novel avian influenza strains.
Researchers said that people born before 1968 were more likely to be exposed to H1 or H2 influenza strains in childhood, making them less susceptible to H5N1, which in in the same virus group. Younger people, however, were more likely to first contract a flu from the H3 subtype viruses, and are less susceptible to H7N9 avian influenza—both are in a second virus group. That's because flu groups contain subtypes that offer cross-strain immunity. In other words, if a person was exposed to an H1 strain in childhood, they have an imprint that helps them fend off avian H5 for life, resulting in a 75% reduced risk of severe illness and an 80% reduced risk of death.
To model this, the authors looked at flu trends from 1918 to 2015 in China, Egypt, Cambodia, Indonesia, Thailand, and Vietnam. The most deadly influenza illnesses occurred when a cohort was exposed to a mismatched avian strain. Thus birth year, and not age, is the most important risk factor for establishing risk for severe disease outcomes.
"For any country with suitable contact and demographic data, the methods shown here can provide rolling estimates of which age groups would be at highest risk for severe disease should particular novel HA subtypes emerge. Such projections could guide cohort- or region-specific prevention, preparation, or control," the authors concluded.
Nov 11 Science study
H5N8 strikes ducks and turkeys in Switzerland, Austria
Today the World Organization for Animal Health (OIE) reported that H5N8 was found in ducks near Kreuzlingen, Switzerland. Kreuzlingen is a village on Lake Constance. The OIE also confirmed that that waterfowl on the Austrian side of the lake had also died from the highly pathogenic avian flu.
According to OIE’s Swiss report, three tufted ducks were found dead in Lake Constance on Nov 4, and virus sequencing showed H5N8, the same H5 clade that's been found in India, Hungary, Austria, Croatia, Poland, Germany, Denmark, and the Netherlands. In their Austrian report, the OIE said 10 ducks on the Austrian shores of Lake Constance also died on Nov 7.
H5N8 targets migratory birds and waterfowl, as well as poultry. Though the virus has not known to threaten human health, it can devastate poultry farms. According to Avian Flu Diary, an infectious disease blog, Austrian officials are now reporting that H5N8 has been confirmed in a flock of free-range turkeys in Vorarlberg, a state near Lake Constance. Last week, 9,000 turkeys in Hungary also died from H5N8.
In other H5 news, South Korea has confirmed H5N6 in the excrement of wild birds. The government report was shared by FluTrackers, an infectious disease news message board. The feces were collected on Oct 28 by a research team from Konkuk University. This is the first time high-path avian flu has been reported in South Korea this winter.
Nov 11 OIE Swiss report
Nov 11 OIE Austrian report
Nov 11 Avian Flu Diary post
Nov 11 FluTrackers post