May 29, 2017
H7N9 Influenza & The Art of War: How a silent killer used us to develop its weapons of mass destruction
Making itself ever more virulent while pretending to be in retreat, the H7N9 virus is an unprecedented threat to China's broiler sector -and the world's people.
By ERIC J. BROOKS
An eFeedLink Hot Topic
||In retrospect, H7N9 avian influenza virus appears to be following Sun Tzu's Art of War: For several years, it studied our weaknesses, making itself stronger while pretending to be in retreat. Having used our own weapons to undermine vaccines and flu treatments, it now reveals itself ready to start a global pandemic.|
Alongside the 579 innocent human lives it has taken since early 2013, China's chronic H7N9 bird flu outbreaks been a business disaster by any measure. Several times since the first outbreak in 2013, it caused China's total broiler flock to fall by 10% to 30% in just months. Four years after the first outbreak happened, China is producing nearly 20% less chicken meat than it did in 2012 and they are eating at least 30% less poultry meat per person than what was expected by this time.
Alongside the countless lost investments in flocks, feed and wet market closures, bird flu stained the entire poultry sector's reputation. Now it seems that the attempts to cure bird flu might have been worse than the disease itself: Scientific evidence suggests that H7N9 is turning into a highly pathogenic microbe. Ironically, it is the bird flu vaccines themselves that appeared to have encouraged H7N9 to mutate and render even human remedies ineffective.
The clue came during this winter's outbreak, which defied conventional, science-based expectations: Natural immunity increases with time and viruses have no interest in killing off their hosts. Consequently, every succeeding pathogenic viral outbreak is usually less lethal than the previous one. That was true of H7N9, which after its initial outbreak, made fewer, milder and less damaging human and livestock outbreaks over the next three years.
Unfortunately, this downtrend was broken with the past winter's unexpected surge in both poultry and human H7N9 cases, with nearly 25% of the latter resulting in fatalities. During this fifth H7N9 outbreak peak period of October through February, Chinese broiler inventories fell by 12%, with AA white feather numbers declining 15% over this time.
Human bird flu cases fared even worse. By mid-2016, the incidence of human bird flu cases and deaths recorded by the World Health Organization (WHO) had fallen by over 80% from their early 2014 peak. The situation seemed to be well under control –until this winter.
From late October through mid-May, the number of chickens infected rose to their highest peak since this strain of bird flu's initial outbreaks. In any given week of the Q4 2016, Q1 2017 or the first two months of Q2 2017, weekly human H7N9 cases totaled 4 to 10 times more than a year earlier.
Not only did this fifth outbreak's human cases exceed the old 2014 record, at 713 cases (as of 26 May 2017), it accounts for nearly half the 1,525 H7N9 infections recorded since the first human case was registered in early 2013. With this outbreak, the number of H7N9 cases and deaths even exceeds those caused by Southeast Asia-based H5N1, which has been wreaking havoc for a decade longer.
During April and May, the number of cases fell, as the outbreak went into its cyclical, seasonal downturn. –But even throughout April and May 2017, new H7N9 weekly cases equaled or exceeded weekly numbers seen during the cyclical peak periods of Q1 2015 and Q1 2016 flu seasons.
Spring time also brought the news that for the first time, H7N9 had been detected at live-bird markets within Inner Mongolia; a province that borders the nations of Mongolia and Russia. This follows the detection of H7N9 in birds in a province on China's southern border into Vietnam. Thus, while all H7N9 cases have been in China up to now, it appears to be only a matter of time before H7N9 begins to infect wild fowl in Southeast Asia and Central Asia, with non-Chinese poultry and human cases to follow.
Even so, it must be said that China's inability to control H7N9 is not due to lax efforts in controlling the disease: Beijing reacted to the latest outbreak far more quickly, farmers vaccinated many more birds and policymakers closed poultry markets more rapidly and for a longer time than in the past. Even when wet markets were closed, cases continued to spread among both people and chickens.
The bad news is that H7N9's rising virulence arises from its evolution into a new strain that resists human vaccines –and we may have accelerated its coming into the world. Guangdong province still accounts for the majority of H7N9 avian influenza virus found in wild birds. Now however, alongside the well-known Pearl River Delta variant of H7N9, a new strain of this avian influenza type is now emerging in provinces bordering on the Yangtze River.
A May 26 report by the University of Minnesota's Centre for Infectious Disease Research and Policy (CIDRAP) states, "Most of the recent H7N9 viruses from China belong to the Yangtze River Delta lineage, which shows reduced cross-reactivity to earlier candidate vaccine viruses, suggesting that stockpiled vaccines made with the earlier virus might not protect against the newly circulating viruses."
It added that, "WHO advisors said two existing H7N9 vaccine strains didn't seem to protect against the new [Yangtze River] lineage, and they proposed the development of a new one." But there's even worse news. The viruses' rapid mutation rate is making its treatment as impossible as its prevention: Researchers discovered that many human cases of the Yangtze H7N9 no longer respond to the commonly prescribed influenza antidote of Tamiflu.
It rapid viral mutation rate has made the world's current stockpile of H7N9 human vaccines and Tamiflu antidote at best only partly effective. Worse yet, vaccines given to broilers may have both accelerated H7N9's development and been responsible for this outbreak's high number of bird flu cases.
The idea that China's own bird flu vaccines could themselves be responsible for bird flu's escalating virulence go back more than a decade –and now feel eerily prophetic. Back in 2005, Robert Webster, an influenza researcher at St. Jude Children's Research Hospital in Memphis, Tennessee, USA concluded that by being only partly effective, "Existing vaccines can only reduce the amount of virus rather than totally inactivating it."
According to Webster, while H7N9 vaccines given to broilers halt the expression of easily visible bird flu symptoms, they do not stop the virus from multiplying, mutating and spreading within poultry flocks. Xinhua News agency quoted Guangdong-based poultry Zhong Nanshan was quoted as stating that, "Existing [broiler] vaccines can only reduce the amount of virus rather than totally inactivating it."
Chinse poultry vaccine's coincident ability to eliminate H7N9 infection symptoms without killing the virus is extremely unfortunate. –All scientific research points to the fact that poultry viruses evolve into strains more lethal to humans when they can circulate in bird flocks for an extended period of time.
By hiding H7N9's symptoms in poultry while giving the viruses a (partly effective) anti-body stress load, China's broiler vaccines have created a perfect accelerator for H7N9's evolution into a lethal virus: One that cannot be stopped by human vaccines or even treated when infection occurs.
Alongside partly effective vaccines, there is one other reason why China has had a much harder time controlling bird flu than Hong Kong did: While China had a policy of only culling visibly infected birds, Hong Kong culled whole broiler flocks even if only one or two chickens fell sick. –When the poultry vaccines masked flu symptoms while allowing the virus to spread and evolve, the limited culling exercises gave H7N9 a perfect breeding ground.
Infected poultry with no H7N9 symptoms is not just the perfect biological for creating new, deadly bird flu strains but is highly effective in spreading it to wild birds and poultry too. Henry Wan, an influenza virologist at Mississippi State University states that, "When vaccinated birds do not have 100% immunity against a particular virus strain, the birds may still be able to infect others with the virus."
Wan explains that, "Because it has some level of immunity, the bird will not show any clinical signs, but it can still shed viruses." All this has been going on –undetected– within billions of Chinese broilers for the better part of ten years. Now that the virus is achieving a critical level of lethality, it may be too late to stop it.
To be fair to China, Hong Kong's solution is not practical for a country of 1.4 billion people. Whereas Hong Kong can kill every chicken in its territory and import 100% of its poultry meat, China's market is simply too large for the world's poultry exporters to fully supply.
This leaves China in a highly awkward position. On one hand, with no country able to export enough chicken meat to feed a population of a billion, it cannot simply cull all its poultry and carry on, like Hong Kong did. On the other hand, the only solution to this situation appears to be a combination of Thai-style compartmentalization of poultry rearing and hygiene.
Wan concurs that, "Raising chickens in confinement minimizes their exposure to wild migratory waterfowl, which have been identified as possible reservoirs of the avian influenza virus. Biosecurity practices also limit exposure of the chickens to unauthorized visitors on the farm." He advocates that, "Flocks are raised as securely as possible, and then are tested for exposure to the avian influenza virus before they are sent to market."
Wan's opinion is backed by the OIE which concluded, that, "Any decision to use [poultry] vaccination must include an exit strategy, i.e. conditions to be met to stop vaccination." This follows research by scientists such as David Swayne of Texas A&M University.
Swayne noted in his study that, "Five countries accounted for 99% of vaccine used: 1) China (90.9%), 2) Egypt (4.6%), 3) Indonesia (2.3%), 4) Vietnam (1.4%), and 5) Hong Kong Special Administrative Region (< 0.01%)… with the exception of Hong Kong, all of these countries remain firmly entrenched with [poultry] viruses after more than a decade of avian flu vaccine use, and none show any signs of looking for the recommended exit."
While going cold turkey and completely discontinuing the use of poultry vaccines might be China –and the world's– only hope of avoiding a serious bird flu epidemic, it is not a pleasant or easy option. With no vaccines, epidemics of H7N9 or newly evolved variants might burn through China's vast poultry population for years. It would probably cause huge financial losses before the H7N9 virus family stabilizes and stops evolving so rapidly.
Between bird flu outbreaks and its ban on US breedstock, China's broiler sector is already literally on its knees. Over the medium term, removing bird flu vaccines from its roster of health care measures can only further undermine this industry's faltering production and profitability.
While China's policymakers have not made any large, definite decisions on this matter, one thing has changed: A recent CDC risk assessment study put H7N9 at the top of the list of pandemic threats from among a dozen bird and animal poultry and livestock viruses. The CDC concluded that H7N9 has the greatest potential for creating a pandemic that would kill millions of people around the world.
In conclusion, H7N9 has brilliantly fooled agribusiness researchers, pretending to retreat and fade away while quietly transforming itself into something too deadly to vaccinate against or treat. Having developed its weapons of mass destruction, H7N9 now literally stands at the edge of China's borders, getting ready to take flight into the surrounding international community.
Do we have the scientific wisdom and political willpower to stop this evolving human disaster? Only time will tell.
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