I hadn’t seen the 2011 American thriller film ‘Contagion’ (with a star-studded cast that includes Matt Damon, Gwyneth Paltrow, Kate Winslet, Jennifer Ehle, Elliott Gould, Jude Law and Laurence Fishburn among others) until now, nine years later, during this lockdown.
It seems eerily prescient of our present situation, and I was impressed at the way several scientific and medical issues were handled and explained to the general viewership.
Take R-naught (R0) or basic reproductive number; an epidemiologic metric used to describe the contagiousness of an infectious agent. The film explained it really well.
An R-naught of above one means that each case is expected to infect at least one other person on average, and the virus is likely to keep spreading. If it’s less than one, a group of infected people is less likely to spread the infection.
A disease’s R-naught value only applies when everyone in a population is completely vulnerable to the disease. This means: 1. No-one has been vaccinated; 2. No-one has had the disease before; 3. There’s no way to control the spread of the disease.
The R-naught for COVID-19 is not even conclusively known as yet, (this is how ‘novel’ the virus is), but is believed to range anywhere between 1.4 and 5.7.
To put that in perspective, the R-naught of pneumonic plague is 1.3 and history tells us just how devastating those outbreaks have been. Comparative R-naughts for other airborne droplet-transmitted diseases are: smallpox 3.5 to 6; measles at a very high 12 to 18; SARS (severe acute respiratory syndrome) 2 to 5; influenza (1918 pandemic strain) 1.4 to 2.8.
The last statistic puzzled me initially. I had read up on the 1918 ‘Spanish’ flu pandemic before writing an earlier column when this lockdown started. The estimated death toll from that virus varied between 17 to 50 million, some citing even as high as 100 million. And this was before the age of air travel and tourism.
That mystery was partly explained in another book I’m reading (the earlier one was Bryn Barnard’s ‘Outbreaks: plagues that changed history’) that focuses on disease outbreaks, and also eerily prescient, ‘Spillover: Animal Infections and the Next Human Pandemic,’ (2012) by American science, nature and travel writer and author David Quammen.
With the 1918 pandemic strain of influenza virus (as indeed with other influenza viruses, which is the rational for the seasonal flu jab), high infectivity preceded symptoms by several days. Quammen calls it “a perverse pattern: the danger, then the warning.” High infectivity among cases, asymptomatic before they experienced the most obvious, debilitating stages of illness explained the mind-numbing scale of that pandemic. “The bug travelled ahead of the sense of alarm.”
Quammen speculated in the 2012 book: “The much darker story remains to be told, probably not about this virus [he was referring then to SARS, where the progress was the reverse, i.e. symptoms tending to appear in persons before, rather than after, those persons became highly infectious] but about another. When the Next Big One comes, we can guess, it will likely conform to the same perverse pattern, high infectivity preceding notable symptoms. That will help it to move through cities and airports like an angel of death.”
Well, his prophesied Next Big One is here, barely eight years after the book. Quammen also accurately predicted it moving “through cities and airports like an angel of death.”
Was Quammen also right about the other bit, high infectivity preceding notable symptoms? The honest answer at this moment in time, with this novel virus, is we cannot say for sure. The CDC (Centers for Disease Control and Prevention) website, updated frequently, states that “preliminary evidence suggests that asymptomatic carriers may contribute to the spread of the disease.” And that, as we know, is the rationale behind our lockdown: better safe than sorry, flattening the curve, and all that jazz.
In an interview shortly after the book was released, Quammen had predicted, ”The world of nature and things we humans are doing ― disrupting ecosystems and then traveling ― those factors are going to be by far the largest measure of our risk.”
The book also underscores how much the field of medicine has expanded since my own undergraduate days in the 1980s. If memory serves correctly, our Microbiology syllabus focused mainly on bacteria, much less so on virology. When we studied about zoonoses (singular zoonosis) or zoonotic diseases, referring to infectious disease caused by a pathogen (an infectious agent, including bacteria, viruses, parasites, prions, etc) that has jumped from non-human animals (usually vertebrates) to humans, the list used to be a relatively short one. Names that I still recall from those days are brucellosis, listeriosis, toxoplasmosis, and of course rabies.
This ‘jump’ from non-human animals to humans is the ‘spillover’ that Quammen and the rest of the scientific community are referring to.
That list of zoonoses has swollen exponentially in the intervening decades, to HIV/AIDS, Ebola, SARS, Nipah virus, MERS (Middle East Respiratory Syndrome), avian flu, swine flu among a dizzying assortment of ‘bugs’ of all sorts.
We’re going to keep encountering all manner of ‘new’ or ‘novel’ zoonoses, which will continue to be a challenge to the scientific community and to governments and populations everywhere because they will be more often than not be “previously unrecognized diseases” and also more likely than not to have increased virulence in populations lacking immunity.
The challenge, as both the film ‘Contagion’ and the ‘Spillover’ book demonstrate, will be to first somehow identify the causative organism, then tracing the reservoir host through retrospectively tracing the index case(s) and their contacts, and then taking measures to contain the spread while frantically searching for a killer drug and/or vaccine. An expensive investment in time, resources, with inestimable suffering to populations due to lockdowns and loss of income (to say nothing of the unconscionable, avoidable suffering our poor migrant and daily-wage workers have been subjected to here), and to laboratory animals (this pandemic alone has probably taken a heavy toll on long-suffering Rhesus monkeys in laboratories around the world in the race to culture COVID-19 and harvest it in the search for curative drugs and vaccines).
Quammen in the same interview termed it a “race” between two factors: On the one hand, the inevitability of further zoonotic spillovers, “many of which could be extremely murderous.” On the other hand, he speaks of the scientific advances being made in public health and the advances in vigilance and response.
Or the more prudent thing would be to learn from this pandemic; learn to respect and nurture wildlife habitats, certainly to stop the wildlife trade, whether for trophy, pelts, tusks, exotic game ‘meat’, aphrodisiac or whatever. We think of this pandemic as terrible and we are living through the hardships it has brought us, to many of us more than others. But The Next Big One could well be much, much worse. It almost certainly will come, the only question is how soon and from where, unless we, all of humankind, sober up and learn a few hard lessons from This Big One.
(An edited version of this article was published on 22 April 2020 in my column ‘On the Upbeat’ in the Navhind Times Goa India)