Photo Credit- CDC
With its exponential growth, high mortality rate, and potential to escape the confines of West Africa, it is admittedly difficult to get anyone to think beyond the expanding Ebola threat right now. Other emerging threats seemingly pale in comparison, but there is nothing that says we are exempt from being forced to fight a viral battle on more than one front.
It wasn’t but five months ago when the outbreak of MERS-CoV on the Arabian Peninsula was capturing headlines, and three months before that, it was H7N9 in China.
While both have receded as threats over the summer, there is little reason to believe that one, or both, won’t threaten again later this fall and winter. And they aren’t alone. Over the past several years we’ve heard plenty of `viral chatter’, from a variety of emerging threats.
Between 2006 and 2008 the biggest pandemic threat was believed to be H5N1 from Asia, but as it turned out, we were blindsided by a North American origin flu pandemic in the spring of 2009.
Few could have predicted this; not only did it emerge on the `wrong’ continent, it came from the `wrong’ host (pigs), and was of the `wrong’ subtype (H1N1).
H5N1 continues to circulate, and remains a legitimate pandemic threat, but a dozen years after it re-emerged in Vietnam it has yet `to figure us out’. For now, it remains primarily a threat to poultry and wild birds.
The H7N9 virus, which emerged suddenly in China 20 months ago, has sparked two winter waves of illness, with the second year’s toll roughly twice that of the first year. Similar to what we’ve seen over these past several months, the virus all but disappeared during the summer months between the first and second wave.
Two Waves of H7N9 - Credit Hong Kong’s CHP
While we can’t know what this fall holds in store for the H7N9 virus, studies released earlier this year (see EID Journal: H7N9 As A Work In Progress), show that the H7N9 avian virus continues to reassort with local H9N2 viruses, introducing new clades of the virus into China’s poultry population.
Last June, in Eurosurveillance: Genetic Tuning Of Avian H7N9 During Interspecies Transmission, researchers working for China’s National and Provincial CDCs, announced that the genetic diversity of the H7N9 virus was even greater than previously described, and that continual reassortment with the H9N2 virus, along with passage through a variety of host species, appears to be influencing its ongoing evolution.
A process the authors call `genetic tuning’.
Remarkably, out of 146 H7N9 viruses with full genome sequences they examined, they detected at least 26 separate genotypes, mostly from the first wave in 2013. Of those 26, twenty were only detected once or twice, suggesting they were transient, and perhaps not as `biologically fit’ as some of the other genotypes.
The authors wrote:
Overall, due to the genetic tuning procedure, the potential pandemic risk posed by the novel avian influenza A(H7N9) viruses is greater than that of any other known avian influenza viruses. A response to this threat requires the combined effort of different sectors related to human health, poultry and wild birds, as well as vigilance and co-operation of the world.
Influenza viruses, because they are spread via droplets, aerosols, and fomites (contaminated inanimate objects like door handles, coffee pot handles, keyboards) – and because carriers can often be infectious prior to showing symptoms – are the type of pandemic threats that keep most epidemiologists up at night.
Last year, in EID Journal: Predicting Hotspots for Influenza Virus Reassortment, we looked at research that ranked eastern China as one of the globe’s top breeding grounds for new flu strains.
And indeed, over the past two years we’ve seen the emergence of no less than four new subtypes (H7N9, H10N8, H5N8, H5N6) from this region that pose significant risks to poultry or human health.
Of course, we are perfectly capable breeding home-grown viruses here in the United States, as we’ve seen one pandemic virus (2009’s H1N1), and a number of swine variant viruses (H1N1v, H1N2v, H3N2v) emerge from pig herds and go on to infect humans (see Keeping Our Eyes On The Prize Pig) over the past decade.
But the close call with SARS in 2003 showed that non-influenza viruses can have `legs’, too.
SARS was a coronavirus, likely with a bat origin, that swept out of China in 2002 and infected nearly 8,000 people worldwide before it was contained. While SARS hasn’t been seen in a decade, a distant cousin – MERS-CoV – appeared in the Middle East in the spring of 2012 and continues to threaten the region, and the world.
Increasingly bat viruses – including coronaviruses, Nipah, Hendra, and Lyssaviruses (including Rabies) – are viewed as emerging or re-emerging human health threats. As if that weren’t enough, over the past couple of years we’ve also seen two new subtypes of influenza identified in bats (see A New Flu Comes Up To Bat & PLoS Pathogens: New World Bats Harbor Diverse Flu Strains).
All things considered, the past 20 years have been a Chiropterist’s delight.
And of course, to this rogues gallery of pandemic threats you can also add any number of influenza subtypes in the wild (including old pandemic viruses like H2N2 and H3N8), the growing ranks of antibiotic resistant bacteria which could prove every bit as deadly as a pandemic, and Virus X . . . the one that isn’t on our radar, yet.
The point here is that once Ebola is contained (I remain cautiously optimistic that it will be, but fully expect it to exact a horrendous cost) the threat posed to global public health by these emerging diseases doesn’t go away. If anything, with our growing population and increasing mobility, the threat grows greater with each passing year.
If fact, we will be lucky if another shoe doesn’t drop this winter while our international efforts are focused primarily on West Africa.
Earlier this year, in Influenza Pandemic As A National Security Threat, we looked at a threats assessment by the Director Of National Intelligence that included:
Health security threats arise unpredictably from at least five sources:
- the emergence and spread of new or reemerging microbes;
- the globalization of travel and the food supply;
- the rise of drug-resistant pathogens;
- the acceleration of biological science capabilities and the risk that these capabilities might cause inadvertent or intentional release of pathogens; and
- adversaries’ acquisition, development, and use of weaponized agents.
Similarly, last year the UK’s National Risk Registry of Civil Emergencies listed Influenza at their nation’s #1 threat.
The highest priority risks
2.2 The following are considered by the Government to be the highest priority risks of emergency, taking both likelihood and impact into account:
• Pandemic influenza – This remains the most significant civil emergency risk. The outbreak of H1N1 influenza in 2009 (‘swine flu’) did not match the severity of the scenario that we plan for and is not necessarily indicative of future pandemic influenzas; the three influenza pandemics of the 20th century (1918–19, 1957–58 and 1968–69) all had differing levels of severity. The 2009 H1N1 pandemic does not change the risk of another pandemic emerging (such as an H5N1 (‘avian flu’) pandemic) or mean that the severity of any future pandemics will be the same as the 2009 H1N1 outbreak.
Somehow we’ve reached the 21st century without truly accepting that a disease threat in one part of the world can quickly become a disease threat for the entire world. We’ve convinced ourselves that vast oceans, border guards and airport screening, and our modern medical prowess can protect us from the ravages of a pandemic.
Nearly halfway into this second decade of the 21st century, we still don’t take global (or even local) public health seriously.
So we continue to gut the budgets of the very organizations and agencies that are on the frontlines, attack disease problems in piecemeal fashion when we can no longer ignore them, and then wonder how a crisis like Ebola can threaten not only Africa, but have repercussions around the world.
I don’t pretend to know what comes after Ebola. I only know that something will.
And unless we get our collective public health acts together, it won’t be pretty. For more on pandemics, and pandemic planning, you may wish to revisit: