The yearly epidemic of influenza virus infections is still months away, but a recent report sheds light once again on the curious nature of this constant companion of humanity.
We have written about the influenza virus many times before, because it is the source of so much suffering, and the reason for the unique need for yearly immunization.
It turns out there are two types of influenza virus epidemics: seasonal and pandemic.
Both only happen because the influenza virus stands alone in its ability to change, every year.
The Seasonal Influenza Epidemics- An Annual December-April Event
What does it mean for a virus to change? Consider the more typical level of change in a virus- none. The measles virus today is essentially the same virus it was 50 years ago, perhaps really unchanged for thousands of years. That’s why if you get measles, you never get it again, you are immune to one virus and if measles every crosses your path again, you will be immune to just that virus. The same is true for chickenpox, for hepatitis B, really for essentially every other virus. We do get many colds, but that’s only because there are hundreds and hundreds of specific cold viruses. Each cold virus can only cause an infection once.
But not so for influenza virus. The actual protein structure of the influenza virus changes, every year. That is because of another twist in the influenza virus story- unlike so many human viruses, it can infect all sorts of animals. Measles, chickenpox, cold viruses, nearly all of them, can only infect humans, because viruses infect by invading the cell, and that invasion requires picking a lock to gain entry. Very few viruses know how to pick more than one lock. But influenza virus can and does.
So in the winter it infects humans, and every spring and summer it changes just enough to pick the lock of all sorts of animal cells, including horses, pigs (swine flu), and cows. It changes a bit to infect the barnyard animals every spring, and then returns, every winter, just a touch different.
That difference renders us susceptible. This December a new strain of influenza virus will arrive in Ohio and across the world, as it does every December. The new strain will cause infection, because our immune systems have never seen it before. But the difference every year is small, so the illness tends to be mild. Yes severe, even fatal infections occur, but way over 99% of people who get the winter influenza infection will recover with no harm done.
That is the story of the seasonal, yearly, influenza epidemics. What about the other type of influenza virus epidemic- the dreaded pandemic?
The Pandemic Influenza Epidemic- Rare, Unpredictable, Deadly
Now and then, when the influenza virus leaves humanity and infects animals, it changes not a little bit, but a lot. Every so often, really not that often, that now very novel influenza virus is still not only able to come back to hit humanity, but spreads well, and kills fiercely.
When all the conditions are right, a pandemic hits humanity.
Those conditions include some of the following:
- The influenza virus infects an animal species and in doing so changes a lot, not just a little.
- The new influenza virus retains the ability to infect people.
- The new influenza virus can spread wildly
- The new influenza virus is deadly.
The most famous influenza virus pandemic took place in 1918. The new form of the virus spread like wildfire and was astoundingly deadly.
Within the one sweep of humanity it infected, this virus went from people to birds and then on returning infected about 1/3 of the entire human species across the whole planet, all within 1-2 years. After the pandemic ceased, 50 million people were found to be killed by this one influenza virus. Fifty million. This stands as one of the deadliest catastrophes by a germ in modern history. https://www.cdc.gov/flu/pandemic-resources/basics/past-pandemics.html
The most recent influenza virus pandemic took place in 2009. That spring, an influenza virus of great novelty appeared first in the United States. It was novel enough that few people had any immunity to it, even if immunized for influenza. About 60 million people around the world got this infection, far fewer than the 33% of humanity in 1918, but still, about 300,000 people were killed by it. https://www.cdc.gov/flu/pandemic-resources/basics/past-pandemics.html
A New Influenza Virus, A Possible Pandemic, China Refuses to Help
The only way to avoid the devastation of a great influenza pandemic like the one on 1918 is to have all the nations of the earth share their influenza virus samples, so that when the big one arrives, we have enough time to make a vaccine, and distribute worldwide.
If that is done, the next pandemic will be controlled. If that is not done, the novel virus may be able to run rampant and kill millions.
Until very recently, the World Health Organization could count on the nations of the world to collaborate, and send it samples of any new or novel influenza virus. Until now.
Now it is reported that a possibly very dangerous novel influenza virus, a possible pandemic virus, has appeared in China, and China is refusing to share the danger, to help the world protect itself. https://www.nytimes.com/2018/08/27/health/china-flu-virus-samples.html
The new influenza virus is not the seasonal influenza virus that will be here in December, it is not spreading widely, and so it is not either a seasonal epidemic or pandemic influenza virus, but one day it might become a true pandemic danger.
The virus in question changed while infecting birds, to a variant known as H7N9. So far, in China, it has infected nearly 800 people, and 40% of them died of the infection, a staggeringly high rate, very suggestive of a dangerous pandemic sort of influenza virus.
What’s missing is that this specific type of influenza virus has not figured out how to rip through millions of humanity. Should it evolve to be able to do that, and retain its deadly potency, a true pandemic could happen.
Now, as long as the World Health Organization has this virus in hand, we can make vaccine for humanity and stave off the catastrophe. If.
- Influenza viruses are distinctive for their ability to change, infect humans, change and infect animals, and return to us changed, and so able to infect us again.
- One sort of way influenza viruses come back to re-infect us is mild, it’s the yearly return of an influenza virus just a touch different than last year. It can cause serious illness, but tends not to, comes every December, leaves every April. It’s the sort of influenza we get flu shots for.
- The other way they come back is far more deadly, far more dramatic, far more rare, and far less predictable, it is the dreaded pandemic. The only way to protect against the catastrophe of a pandemic is for every nation to share its samples of novel, emerging, non-seasonal influenza viruses.
- China has violated this approach, putting all of humanity outside of China at risk, unable to create a vaccine should the virus that killed 40% of the nearly 800 infected gets loose and goes global.
Fortunately, pandemics are rare and infrequent, too many conditions have to go wrong in just the right way, and we do have the World Health Organization ready to create vaccine if a pandemic threatens. Let us hope we can return to being able to do that.
To your health,
Dr. Arthur Lavin