No, We’re Not About to See ‘Contagion’ Come True

You may have seen the news that everyone is starting to stress-watch Steven Soderbergh‘s Contagion. The surface parallels are indeed striking:

1. In the film, emerging virus Meningoencephalitis Virus One (MEV-1) infects patient zero, Beth Emhoff (Gwyneth Paltrow), at a live animal meat market in Hong Kong. The 2019 Coronavirus traces back to a market in Wuhan.

2. The fictional MEV-1 traces back to a bat, with a swine intermediary. The real-world 2019-nCoV came from a bat, and most likely transferred to another species before making the jump to humans, although as of this writing, there’s no real consensus on what that intermediary might have been. Still, there are some notable differences on this front. The 2019-nCoV virus is a coronavirus, like MERS or SARS before it. The film’s MEV-1 is modeled as after the hypothetical evil lovechild of influenza and a Nipah virus, an unholy combination that we thankfully have no reason to worry about so long as no evil mad scientists get any ideas because there’s no way that shit can happen naturally.

That said, with regard to why MEV-1 shouldn’t leave you freaked out about 2019-nCoV, the most important thing we need to talk about is a term you’re already familiar with if you’re one of those people who stress-watched Contagion recently: R0.

As Epidemic Intelligence Service Officer Dr. Erin Mears (Kate Winslet) explains in the movie, R0 (pronounced like “R-naught”), or basic reproduction number, refers to the average number of new cases a single infected individual creates. In other words, how many formerly healthy people catch the disease through contact with one sick person. Dr. Mears’ explanation of the concept is pretty legit, as is most of Contagion in terms of accuracy. But it’s a simplified version, and the nature of that simplification has decided ramifications.

The thing about R0 values is that they are averages. And to explain why that makes a difference, we need to talk about Coronaviruses. Before 2019-nCoV, the most notorious Coronaviruses were MERS and SARS. MERS, or Middle East respiratory syndrome, has had several small outbreaks since it was first discovered in 2012, and while very severe in terms of mortality (the case fatality rate is around 30 to 40 percent), the virus’s R0 is very low.

And then there’s SARS. If you’re wondering what a SARS is, you are probably a Gen Z-er, and the answer is “something before your time.” Because while SARS, or Severe Acute Respiratory Syndrome, caused a huge uproar in its heyday of 2002-3, good old fashioned quarantining ultimately went a long way, and the virus is now considered functionally extinct.

While you’d have a better chance of surviving SARS than MERS (the case fatality rate of the latter was somewhere between 9 and 16 percent) it was considerably more adept at spreading person-to-person. At least, kinda. The weird thing about SARS was it displayed a pattern of “super-spreaders” — a select group of individuals, for reasons scientists don’t fully understand, were incredibly contagious.

Most people infected with SARS did not infect anybody; a select bunch infected dozens. At least one super-spreader infected over 100. It’s a weird quirk, but not unheard of. So the original projected R0 for SARS was between 2 and 4, and everybody panicked. One research team that later went back and factored out super-spreaders found that in their absence the R0 was more like 0.4, so containing SARS proved to be a matter of identifying and isolating super-spreaders as quickly as possible, which is a far more manageable task than a scenario where R0 is around 2 and all infected individuals prove more or less equally contagious — the maximum difficulty scenario that Contagion runs with.

The epidemiologist Dr. Maia Majumder shared a very helpful figure illustrating this point on Twitter recently:

Friendly reminder about #nCoV2019 transmissibility estimates from the past day:

The basic reproduction number (R_0) is an *average*. An R_0 of 2 doesn't necessarily mean that every case will infect 2 other people. In fact, here are 3 (non-exhaustive) scenarios in which R_0 = 2. pic.twitter.com/EqaXy1puyW

— Dr. Maia Majumder (@maiamajumder) January 24, 2020

Contagion treats the spread of disease as if an R0 value inherently plays out like the top row, Scenario 1. Which is, from an epidemiological perspective, a hell of a lot more difficult to contain than the second row, Scenario 2. Which is a lot more like how SARS ultimately played out. That SARS and 2019-nCoV come from the same family of viruses doesn’t mean the new arrival necessarily follows in SARS’ footsteps, but it does call into question the logic behind immediately jumping to the worst-case scenario on this front.

Thankfully for our continued existence as a species, diseases tend to be either highly infectious or lethal but not both at the same time. The thing is there’s really no evolutionary pressure pushing viruses towards that worst-case nightmare scenario. Viruses need hosts to live, so if they murder all potential hosts they lose in the end, too.

And that actually brings us to one more point about Contagion that’s worth discussing: even by its own definition of the fictional MEV-1 virus, the picture it paints is decidedly bleak. While the film often cites the MEV-1 case fatality rate at around 25 percent, basically every named character who gets sick over the course of the film dies.

Blogger conman Alan Krumwiede (Jude Law) gets sick and recovers, but the film indicates that he had no viral antibodies in his body and therefore came down with some other kind of respiratory infection. As such, the first cough and the final death rattle become synonymous in Contagion. It’s a case fatality rate of 25 percent depicted more like >90 percent.

The reported case fatality rate for 2019-nCoV, meanwhile, currently stands at around 4 percent. It’s serious, of course, and authorities are right to take aggressive precautions to contain the spread, but Contagion is, and will continue to be, a non-prophetic work of fiction.