Monday, March 30, 2020

Unintended Consequences? Polio and COVID 19

Polio children in iron lungs

We must consider the unintended medical consequences of societal lockdowns hoping to prevent the spread of COVID 19. Unintended consequences are exemplified by past polio epidemics that left some of my classmates crippled. For the most severely afflicted, a polio infection required, not a ventilator, but an iron lung for children to breathe. The polio virus had likely been around for thousands of years, but in the 20th century severe epidemics began. Why?

In 1992 Dr Krause from the National Institute of Health published, “There are numerous examples of old viruses that have caused new epidemics as a consequence of changes in human practices and social behavior. Epidemic poliomyelitis emerged in the first half of this century when modern sanitation delayed exposure of the virus until adolescence or adulthood, at which time it produced infection in the central nervous system and severe paralysis. Before the introduction of modern sanitation, polio infection was acquired during infancy, at which time it seldom caused paralysis but provided lifelong immunity against subsequent polio infection and paralysis in later life. [emphasis mine] Thus, the sanitation and hygiene that helped prevent typhoid epidemics in an earlier era fostered the paralytic polio epidemic.”

Indeed, it was the more affluent people with higher standards of living that were most affected by polio epidemics, because their children were more likely isolated from milder strains.

As is the case for most rapidly mutating viruses, there will be various strains. Some will cause mild effects while others could be deadly. A strain’s virulence may depend on a person’s age and health. There are several strains of influenza virus, so vaccines are adjusted each year. There were 3 strains of poliovirus that were identified. Vaccinations eradicated two types and now groups like the Rotary are funding work to eradicate the remaining type. The observation that early exposure to polio viruses provided life-long immunity raises the question regards dealing with COVID 19. To what degree is sheltering in place preventing people from becoming naturally immune when infected with a mild strain?

The larger the population of naturally immune people, the greater the “fire-break” that prevents the spread of a more deadly strain. Just as social distancing minimizes the exponential growth of a deadly strain, it also prevents the exponential growth of naturally immune people. If so, perhaps a more targeted approach would be better. Our elderly population are the most vulnerable and are often confined to crowded facilities. People with compromised health conditions should self-isolate. We definitely need to minimize the spread to those vulnerable people. Perhaps designating one hospital to specialize on COVID and another for non-COVID medical care is a good strategy. Stopping medical care for a far greater number of people with other severe problems out of fear of spreading COVID 19 is not wise. And is it wise to quarantine everyone?

The fact that many people have tested positive for COVID 19 virus but had no symptoms suggest there are various mild strains that could naturally impart immunity. These mild reactions are primarily seen in people younger than 50 years old. However, once those younger cohorts gain immunity, they will be less vulnerable as they age.  

Recently in the New England Journal of Medicine Dr Fauci wrote, " If one assumes that the number of asymptomatic or minimally symptomatic cases is several times as high as the number of reported cases, the case fatality rate may be considerably less than 1%. This suggests that the overall clinical consequences of Covid-19 may ultimately be more akin to those of a severe seasonal influenza (which has a case fatality rate of approximately 0.1%) or a pandemic influenza (similar to those in 1957 and 1968) rather than a disease similar to SARS or MERS, which have had case fatality rates of 9 to 10% and 36%, respectively."

Dr John Ioannidis is a Professor of Medicine, of Health Research and Policy and of Biomedical Data Science, at Stanford University School of Medicine, director of the Stanford Prevention Research Center, and co-director of the Meta-Research Innovation Center at Stanford

In contrast to Imperial College model suggesting over a million Americans could die, Ioannidis argued, “If we assume that case fatality rate among individuals infected by SARS-CoV-2 is 0.3% in the general population — a mid-range guess from my Diamond Princess analysis — and that 1% of the U.S. population gets infected (about 3.3 million people), this would translate to about 10,000 deaths. This sounds like a huge number, but it is buried within the noise of the estimate of deaths from “influenza-like illness.” If we had not known about a new virus out there, and had not checked individuals with PCR tests, the number of total deaths due to “influenza-like illness” would not seem unusual this year. At most, we might have casually noted that flu this season seems to be a bit worse than average.”  The Imperial College and Ioannidis’s model will be tested soon, as American COVID deaths stands at 2,871 as of March 30th.

Nonetheless, it will be difficult to determine how effective a societal lockdown was if COVID 19 behaves like influenza.  Flu infections dramatically drop beginning around April. Relative to seasonal warming, a lockdown may have a minimal effect. Perhaps by inhibiting the spread of a natural immunity, we may be setting the stage for another big wave of COVID 19 next year. These are questions must be debated.

Influenza deaths versus seasons

Jim Steele is Director emeritus of San Francisco State’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism