"...experts are looking to the sixth wave with some trepidation".
There are quite a few bullet points in this article that are disturbing on their own, but taken in the context of this article, the sheer number of significant developments in the last year is downright scary. I was going to list them, but it would mean quoting practically the entire article, as each paragraph has something significant to say about the way H7N9 has changed in the past twelve months.
H7N9 Flu Changes Worry Experts
'Huge surge' in cases in China in 2016-17 season
SAN
DIEGO -- Flu experts are watching China uneasily these days after some
unsettling changes in the H7N9 avian influenza A strain during the
2016-17 epidemic in that country.
The fifth wave of the virus, which was first seen in humans in 2013,
saw a "huge surge in cases," the CDC's Tim Uyeki, MD, told a symposium
here at the annual IDWeek meeting, sponsored jointly by the https://www.idsociety.org/Index.aspx" rel="nofollow - Infectious Diseases Society of American (IDSA), the https://www.pids.org/" rel="nofollow - Pediatric Infectious Diseases Society (PIDS), the http://www.shea-online.org/" rel="nofollow - Society for Healthcare Epidemiology of America (SHEA), and the http://www.hivma.org/Home.aspx" rel="nofollow - HIV Medicine Association (HIVMA).
After the first year, Uyeki said, the case totals in following
seasons were roughly stable or declining, but the fifth saw some 764
cases, almost half the cumulative total of 1,562 over all 5 years,
according to the World Health Organization.
But what worries the experts is not just the numbers. After 4 years
of relative stability, the virus began to show changes during the most
recent wave, including a newfound ability to escape vaccines and to
resist antiviral drugs, Uyeki said.
As well, the virus was seen in a greatly expanded territory and began
-- for the first time -- to cause illness in the birds it infects.
For those reasons, a new CDC model -- the https://www.cdc.gov/flu/avianflu/h7n9-virus.htm" rel="nofollow - Influenza Risk Assessment Tool -- puts H7N9 at the head of a list of animal flu strains that might cause a pandemic among humans.
In the first four waves, the virus was mainly borne by poultry (who
were unharmed by it) and the way people caught it was by exposure to
infected birds, often in large poultry markets. There was some
human-to-human transmission but it was not easy. When clusters of cases
emerged, it was usually because of exposure to a common avian source,
rather than transmission among people.
Still, most reported cases resulted in hospital admission and some
40% of admitted patients died, Uyeki said. "That's been consistent since
2013," he told MedPage Today, "and 40% is extremely serious illness."
But in 2016-17, Uyeki said, the virus showed "significant antigenic
drift" to the point where the experts said it no longer belonged to the
older Pearl River Delta lineage, but now merited a new name -- the
Yangtze River Delta lineage.
The new lineage was "no longer well controlled" by the vaccines that
had been developed to protect against the earlier lineage, he said, and
roughly 10% of isolates now showed markers of resistance to the main
class of anti-influenza drugs -- the neuraminidase inhibitors. In
earlier years such markers had been seen in about 4% of isolates.
As well, late in the season, the virus suddenly started to kill
infected birds. From a "low pathogenic" avian flu, it had become "highly
pathogenic" and 10 Chinese provinces saw outbreaks among their poultry
stocks.
There is little data yet on how that change will affect people --
Uyeki said there have only been 28 recorded human cases so far -- but
experts are looking to the sixth wave with some trepidation.
On the positive side, if
the virus affects birds, it will be easier for health officials to
follow outbreaks and perhaps to take preventive measures, commented Andy
Pavia, MD, of the University of Utah, who moderated the session at
which Uyeki spoke.
"It would be a lot easier to track and control the high-path species because at least you know where to look," Pavia told MedPage Today.
How humans will be affected is the open question, he said, noting
that "the changes that make it high path for birds are not the same as
those that make it more transmissible among humans."
One thing that's important for a flu virus to spread efficiently
among people is the ability to bind to receptors in the upper airway.
Seasonal influenza strains have that ability but usually have a low case
fatality rate. The highly pathogenic H5N1 avian flu binds only to
receptors in the lower respiratory tract and so only rarely infects
people but kills 60% of the people it does infect.
The H7N9 flu lies somewhere in the middle, Uyeki said -- it prefers
receptors in the lower respiratory tract but can bind to those in the
upper regions.
"In general," Pavia said, "everybody in the flu field is worried about the fifth epidemic."
"There's spread to a much larger area in China, it's still causing a
lot of cases in areas where they've done a pretty god job of trying to
clean up the poultry markets, and the sheer numbers makes you wonder
what's coming next."
https://www.medpagetoday.com/meetingcoverage/idweek/68339" rel="nofollow - https://www.medpagetoday.com/meetingcoverage/idweek/68339
------------- "Buy it cheap. Stack it deep" "Any community that fails to prepare, with the expectation that the federal government will come to the rescue, will be tragically wrong." Michael Leavitt, HHS Secretary.
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