Saturday, March 4

Vaccine developers race to outpace reassortments in H7N9 flu virus

"... the virus has split into two distinct genetic lineages, with a new branch of the virus family now emerging in the current epidemic ... That has rendered the H7N9 vaccine stockpiled by the United States less effective against the newly emerging branch ..."

Is the latest bird flu outbreak in China another false alarm? The thing about these viruses is that they're a false alarm until suddenly they aren't. The doomsday virus can emerge virtually overnight, even though the chance of this kind of virus emerging from a reassortment of less deadly strains is low.

My hope, which I've expressed once before on this blog, is that the unprecedented number of humans, mammals, and birds at this time is its own inoculation against a doomsday virus.

Viruses are always reassorting with each other and as these 'mutations' infect larger and larger numbers of hosts in a pandemic scenario, they tend to weaken rather than strengthen in their deadliness. 

 Of course there could be a blip where a virus actually grows in strength. And even if the theory holds, there could still be a huge number of human deaths from a pandemic before the virus weakens to the point where its deadliness subsides to a normal range for influenza viral infections -- all of which, by the way, are actually "bird" flu viruses, whether transmitted by humans, pigs, etc.

In short the dreaded doomsday virus, projected to be so virulent that it quickly kills virtually every host, might never come about, at least not in the present era of megapopulations. 

 But as we saw with the 2009 swine flu, which in a matter of hours went straight from the outbreak stage to the pandemic stage, scientists and health agencies can be caught napping.

With the exception of China's state health agency, the experts refused to believe at first what was happening, firstly because it had never happened before, secondly because it flew in the face of their mathematical models about how a highly infectious viral outbreak acts, and because they were positive that the next flu pandemic would come from China. 
They couldn't wrap their minds around the idea that it could come from a commercial pig farm in Mexico.

So the international/government health agencies were slow to react when a private-sector American biosurveillance company reported an alarming mystery disease outbreak in Mexico.  

By the time the CDC and WHO realized what had happened it was too late. 
If the Chinese had not ignored CDC and WHO; if they hadn't battled swine flu at their international airports, which slowed by a few days the inevitable exponential spread of the virus in China and nearby countries; if several other countries had not quickly adopted the Chinese model of fighting the virus (as against the WHO-CDC model); and if the Chinese had not worked miracles to get a vaccine into record-fast production and distribution, I do not want to imagine what the human death toll from that pandemic might have been.

But that thing is still out there, still killing people, still reassorting with other viruses.

As to the super-vaccine pharmaceutical companies are trying to develop, the one guaranteed to protect against every possible reassortment of bird flu -- reference "War of the Worlds." The human immune system already has so little to battle that it's getting weaker. So all bets against a doomsday infection could be off, if the immune system becomes such a wuss that a paper cut can kill it. Oh but wait that's already happened.

My view is that the super-vaccine is one of those ideas that is only good on paper.

Surge in human cases of deadly bird flu is prompting alarm
By Lena H. Sun
3 March 2017 - 11:00 AM EST
The Washington Post

“This is a virus you don't want to take your eyes off"

A surge in human infections of a deadly bird flu in China is prompting increasing concern among health officials around the world. While the human risk of these outbreaks is low at the moment, experts are calling for constant monitoring because of the large increase in cases this season, and because there are worrisome changes in the virus. U.S. officials say of all emerging influenza viruses, this particular virus poses the greatest risk of a pandemic threat if it evolves to spread readily from human to human, according to a report released Friday.

Centers for Disease Control and Prevention officials are developing a vaccine that would target a newly evolving version of the virus.

China is experiencing its largest outbreak of the H7N9 bird flu strain, with at least 460 infections reported since October. About a third of people diagnosed with H7N9 have died of their infections, according to the World Health Organization. Human infections with this type of bird flu were first reported in China in March 2013, and since then, there have been yearly epidemics of human infections.

But this winter, the number of cases is greater than any of the previous four seasons. This year's infections account for more than a third of the 1,258 H7N9 cases that have been reported since 2013. Most human infections involve exposure to live poultry or contaminated environments, especially markets where live birds have been sold. During the previous four waves of H7N9, 88 percent of patients developed pneumonia, 68 percent were admitted to an intensive care unit and 41 percent died, according to a report from the CDC.

“This is the virus we were concerned about in 2013, and now we're seeing these increasing number of cases,” said Daniel Jernigan, who heads the CDC's influenza division, in an interview this week. “This year it came back much stronger, so the numbers of cases we're seeing has already surpassed all the other waves, and the season isn't even over yet.”

In addition, the virus has become more deadly to poultry, which might lead to more severe infections in humans, he said. For all those reasons, officials are watching developments closely.

“This is a virus you don't want to take your eyes off,” he said.

Among a dozen animal and bird viruses that are not yet circulating widely in people, the H7N9 virus has the greatest potential to cause a pandemic, according to the CDC. That assessment is based on the virus's ability to spread easily and efficiently to people from animals and its ability to cause serious disease.

On Wednesday, WHO officials in Geneva said the risk of sustained human-to-human transmission of H7N9 remains low. The characteristics of the infections and case fatality rate remain similar to previous waves, officials said.

But “constant change is the nature of all influenza viruses,” Wenqing Zhang, who heads WHO's global influenza program, told reporters during a media briefing Wednesday. “This makes influenza a persistent and significant threat to public health.”

One change already underway is that the virus has split into two distinct genetic lineages, with a new branch of the virus family now emerging in the current epidemic, officials said.

That has rendered the H7N9 vaccine stockpiled by the United States less effective against the newly emerging branch, officials said. The CDC is developing an influenza seed virus that can be used by vaccine manufacturers to produce another H7N9 vaccine to match a newly emerging H7N9 strain.

It will take several months to produce and test a new vaccine, a process that will get underway in June and July after vaccine manufacturers complete their work on making seasonal flu vaccine.

Vaccines to protect first responders against the highest-risk bird flu viruses are part of the pandemic flu stockpile maintained by the Biomedical Advanced Research and Development Authority, the agency within the Department of Health and Human Services responsible for providing medical countermeasures to human-made and natural threats, including pandemic influenza and emerging infectious diseases.

Rick Bright, director of BARDA, said manufacturers will be producing enough vaccine to provide 40 million doses, enough to vaccinate 20 million people, he said.

[Outgoing CDC chief talks about his greatest fear: pandemic influenza]



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