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I’ve been idly following along as the CDC reports on the Wuhan coronavirus, 2019-nCoV. Why? I write science fiction (sometimes) and I’ve been fascinated by the intersection of history and catastrophe for a long time. I like to follow news stories like this one so that if I ever choose to write a pandemic-apocalyptic piece I could do it with at least a scrim of realism (which is often all you really need: a few authoritative phrases to toss about, some nifty numbers, and readers’ left brains think, Oh, this writer knows what she’s doing, and relaxes, after which you can tell them anything). But a funny thing happened on the way to the story file: I started doing my own calculations based on the raw data, and my interest sharpened.

As of right now (17:30 UTC-8, 26 January 2020) the 2019 novel coronavirus (2019-nCoV) has an infectivity rate, or R0 (pronounced R-zero) of 2.6 and appears to be accelerating. (For comparison, the flu pandemic of 1918 had an R0 = 2, and ordinary seasonal flu = 1-2.)

The 2019-nCoV fatality rate (the number of people infected who subsequently die of the virus) = 4%. (1918 flu pandemic = 2%, seasonal flu = <0.1%.)

The 2019-nCoV incubation period (the time from when a person comes into contact with the virus and begins to show symptoms) = 1-14 days, averaging about 10. (Seasonal flu = 1-4 days, average about 2, 1918 pandemic = unknown, though if it’s similar to H1N1 of a few years ago, around 5 days.) And there are indications that, like flu, those who have contracted the virus are infectious even before showing symptoms. This is Bad News: infected people will be spreading the virus without knowing they’re even infected, and they’ll be doing it five times longer than those with seasonal flu and twice as long as the 1918 pandemic.

So, to recap, this new virus is more infectious than the H1N1 strain of flu that killed 50-100 million people a century ago, it is much more deadly, and it will be spread farther and wider by asymptomatic people. It makes ordinary, seasonal flu (that killed about 80,000 people in the US alone in the 2018 flu season) look like a startled sneeze.

These are preliminary figures; the data we have is so sketchy as to be mostly useless. We simply have no idea what the real picture is; it’s entirely possible that things aren’t nearly as bad as they seem. On the other hand, they could be worse. I think we’ll know a lot more in 10-14 days. Meanwhile, expect those numbers to vary enormously as other regions begin to track cases with varying degrees of accuracy and transparency. If R0 and fatality numbers go up, I’ll be stocking up on masks and gloves and dry goods and batteries and wine (oh, lots of wine), and not letting anyone in the house without a mask. If the numbers start to go down, well, I’ll still stock up—masks and water don’t go bad, and lithium ion batteries and wine last a while—but I’ll be a lot more relaxed about it.

Am I being alarmist? No doubt. But I’m a big fan to planning for the worst and hoping for the best. Your response, of course, may vary.