Films, Infections and Covid. 22.05.20
Or: ‘All you need to know about pandemics from the movies’.
Welcome to The Plague Pit – issue number 22. Our guest contributor for this issue is Dr John Goldstone. John is an eminent intensive care specialist with an encyclopaedic knowledge of film. In a zombie apocalypse, he’d be the right man to have by your side with the first aid kit.
The Covid epidemic has re-introduced all sorts of medical terms which only a few weeks ago we were quite unfamiliar with, from the term outbreak (an increase in infection above the background rate locally), an epidemic (a large spike of infection in a region), and pandemic (an epidemic with a passport) Whilst these terms, and the way in which infectious disease behave, have been forgotten in 2020, in the 20th century, and certainly in the 19th century the effects of infectious diseases were everyday. Luckily we do not have to delve into Google Scientific to re-learn key points: we simply need the actress Kate Winslet (Contagion 2011) to explain and then watch selected movies instead.
Infectious diseases were a common event in previous times, sweeping over countries and ravaging the population. The great Cholera epidemic in 1832 affected Provence, and is the backdrop of Le Hussard sur le Toit, Our heroine, Juliet Binoche, the wife of a Count, is in Aix, it is a hot summer, and the infection will cut her off and leave her stranded. Not only that, but Italian revolutionaries and Austrian spies will help spread the disease, spread sedition, and spread assassination. In order to escape Juliette sets off across country, helped and hindered by Olivier Martinez, a proud Italian chevalier.
Now cholera is caused by the bacterium Vibrio Cholerae, and was known as the ‘Blue Death’ back in the day. We become infected by the oro-faecal route, from not washing hands, a disgusting but common habit. Apparently only 19% hand wash with soap after a loo stop world-wide, so we can forgive the poor peasants of Provence. The wise physician uses alcohol on his hands, which is ignited in a dramatic cleansing routine. Actually this is difficult to do, as anyone lighting Christmas pudding can tell you, but we can forgive the film that point.
The film has large numbers of fatalities, and today the little Vibrio germ causes 100 000 deaths per year worldwide. In Provence, Binoche is subjected to several control measures. She originally socially isolates when the disease hits. And she has a liking for English tea, boiling the water, and killing the Cholera which is spread via the water supply. When on the move with our hero, Olivier Martinez, they are rounded up by the authorities, and mixed up the infected. It seems that it spreads quickly through the camp, and indeed it does. The reproductive rate, or R0, is between 1.5 to 3, meaning that a sufferer will pass the disease to at least 1.5 other individuals. Lastly, only the few survive Cholera, and that’s correct: the Case Fatality Ratio is up to 60%, meaning that 60 out of 100 people with Cholera at that time would die. The good news was both Binoche and Martinez survived Cholera and the adventure to get her home. Sadly though, Martinez does not win her heart.
Infectious diseases feature often in feature films. Pneumonic Plague (best known as the Black Death, caused by the bacterium Yersinia Pestis and spread by fleas and rodents) comes to New Orleans in Panic in the Streets, the 1950 noir movie which sees a gang member arrive via boat, who then infects the criminal gang and then potentially the city. Plague has an untreated mortality rate close to 100%, so the heat is on for our star doctor, Richard Widmark.
Whilst Plague is lethal, it has a low reproductive rate of 1.0 (R1), meaning that one infected person infects 1 other on average. Because of this, and providing fleas and rodents are not ubiquitous, the primary method to contain the infective outbreak is finding the individuals, and isolation and prompt treatment with antibiotics. Hence our doc lines up the contacts and gives them a ‘jab’. By cornering the perp, R0 drops quickly and the outbreak stops.
Knowing how infection spreads enables us to plan a strategic approach to best treat the epidemic. We use a mathematical model of diseases and it can be a complicated science, so thank goodness we have celluloid to help us explain and illustrate. For this we need a simple dramatic outbreak of infection, and the plot of a Zombie movie needs no explanation. The cause of a Zombie infection includes virus’s (World War Z), bacteria (Deck Z) and even fungi (The Last of Us)! The transmission is mainly due to biting, but also include airborne spread, or horrible slavering bodily fluids. Everyone is familiar with the idea’s of the outbreak: a Zombie can infect several people, it takes time to became infected, rare people like Will Smith (I Am Legend) are immune, and Zombie’s do not live forever and generally die after a certain time.
With that in mind, we can start to model the Zombie epidemic: we could start with groups, such as susceptible individuals, Zombies and Zombies who have died. Such a model (SZR type) has three compartments. From there, we add complexity to the model by adding further compartments or group, such as infected humans, not yet Zombies, and a compartment representing individuals who are hiding from the Zombie attackers. Additionally, we could have a group of Zombies that have been killed by the susceptible individuals.
If we know the numbers of people each Zombie infects (sounds like R0…) and include some time frames for the rate of infection and the time a Zombie lives for, a simple model (SZR type) can predict a depressing future. If a zombie finds one person each day, and has a 90% chance of infecting a person, in 100 days only 273 humans are left from the who population (> 7 billion), leaving each person outnumbered by 1 million Zombies. However, in the more complex model, where the human race fights back, and a birthrate is included, hope returns and Zombies can be defeated!
What about Covid-19? Our statistics so far suggest an incubation period (time from infection to the appearance of symptoms) of 2-14 days, with outliers of up to 27 days. The reproductive rate, R0, has been reported between 1.5 to 3, and this estimate varies. For other respiratory virus’s, Seasonal Flu has an R0 of 1.3 and for SARS it is 2.0. We do not know what the case fatality rate is for Covid-19 yet, as we do not know reliably what the total number of infected patients is: we haven’t been testing everyone yet, still less following up all the infected tests with the outcomes. We do know that fatality is mainly confined to the over 45 year olds, and if you are between 0 and 17 years old the mortality is 0.04%. This is 4 in 10 000, or 1 in 2500.
To put this all in context, throughout the 19th Century, outbreaks of cholera deaths occurred during the summer months in London and many other cities in Europe In the worst years, in London alone Cholera fatality would be greater than UK Covid. Until of course Dr John Snow concluded that cholera deaths were distributed around the water supplies, the communal outdoor water pump. He removed the pump handle, stopped those around drinking infected water, and the outbreak went down fast. Perhaps our ‘John Snow moment’ has already happened through isolation and social distancing, R0 is falling, and we are hopeful of a vaccine to prevent further outbreaks. Oh, and we can also look forward to several films from the epidemic stable too.
Dr John Goldstone
References
Contagion (2011). The Horseman on the Roof (1995). Panic in the Streets (1950). World War Z (2013)
Cholera Epidemics of the Past Offer New Insights Into an Old Enemy: The Journal of Infectious Diseases 2018;217:641–9
Gani R, Leach S. Epidemiologic Determinants for Modeling Pneumonic Plague Outbreaks. Emerg Infect Dis. 2004;10(4): 608-614. https://dx.doi.org/10.3201/eid1004.030509
Equations of the End: Teaching Mathematical Modeling Using the Zombie Apocalypse J Microbiol Biol Educ. 2016 Mar; 17(1): 137– 142.
https://www.worldometers.info/coronavirus/coronavirus-age-sexdemographics/
J R Soc Interface. 2011 May 6; 8(58): 756–760 Herald waves of cholera in nineteenth century London