Study identifies H7N9 mutations that could ease spread among humans
Researchers looking for mutations that might make H7N9 avian influenza more easily transmissible among people identified three amino acid changes that would make the virus more likely to bind to human airway receptors. A team of researchers from the United States, including those from The Scripps Research Institute, and the Netherlands reported its findings today in PLoS Pathogens.
The scientists focused on mutations that could occur in the H7 hemagglutinin (HA) protein, which allows the virus to latch onto host cells. They didn't test the mutations in H7N9 viruses, because of gain-of-function rules and concerns. Rather, they used molecular modeling and knowledge of the HA structure to flag mutations that have the capacity to make the virus more specific to human, rather than avian, airway receptors. Then they produced an HA with different combinations of the mutations in an experimental cell line (not H7N9) and tested how strongly they bound to human and avian receptors.
The team found that mutations in three amino acids bound more strongly to human receptors, signaling a specificity switch from bird to human types. In another experiment, they found that the H7 mutants also attached to cells from human tracheal tissue.
The researchers concluded that understanding the mutations that might allow the virus to spread more easily in humans is a useful tool for surveillance in poultry and humans, as their identification may serve as an early warning.
Jun 15 PLoS Pathog study
Spanish study finds no reduced flu vaccine effect in consecutive seasons
As opposed to results of recent studies from Canada, findings of a study from Spain published yesterday indicated that getting immunized against influenza does not lower the protective effect of flu vaccine in the subsequent season.
Writing in PLoS One, investigators noted that their test-negative case-control study included data on patients 9 years old and older from the 2010-11 flu season through the 2015-16 season. It included 1,206 cases of 2009 H1N1 flu, 1,358 H3N2 cases, and 1,079 influenza B cases.
They found a flu vaccine effectiveness (VE) across the seasons of 53% for H1N1 for persons vaccinated in the current season only, compared with a 50% VE for those vaccinated in both the current and previous seasons. For H3N2, VE rates were 17% and 3%, respectively, and for flu B 57% and 56%, respectively.
The authors conclude, "Our results suggested no interference between the previous and current influenza vaccines against A(H1N1)pdm09 and B viruses, but a possible negative interference against A(H3N2) virus."
Jun 14 PLoS One study
Feb 10 CIDRAP News story "Studies shed light on effects of serial flu shots, current vaccine's benefits"
Apr 5, 2016, CIDRAP News story "Prior-year vaccination cut flu vaccine effects in 2014-15"
DRC, Belgium, Nigeria report more avian flu outbreaks
The Democratic Republic of Congo (DRC) yesterday reported 11 more highly pathogenic H5N8 avian flu outbreaks, all in village ducks and chickens in Ituri province, according to a report to the World Organization for Animal Health (OIE).
The location of the latest outbreaks is the same area in the DRC's northeastern corner where H5N8 was initially reported in late May, which signaled the DRC's first outbreaks involving the subtype. Over the past few months H5N8 has turned up in a handful of African nations.
The new events had start dates ranging from May 17 to Jun 3. The virus killed 6,927 of 17,272 susceptible birds, and the survivors were slated for culling.
In other H5N8 developments, Belgium reported three more outbreaks in wild birds, officials said today in an OIE notification. The events began from Jun 13 to Jun 15, affecting locations in Luxembourg, Hainaut, and West Flanders provinces. The virus killed 45 of 101 susceptible birds, and the rest were destroyed as part of the response measures.
The outbreaks follow a Jun 2 report of an outbreak involving a family of birds that includes pheasants and quail.
Elsewhere, Nigeria reported one new H5N1 outbreak in backyard poultry, according to a report today from the OIE. The event began on May 15 in Adamawa state in the east, killing 50 of 200 layers.
Jun 14 OIE report on H5N8 in the DRC
Jun 15 OIE report on H5N8 in Belgium
Jun 15 OIE report on H5N1 in Nigeria