The Deceptively Simple Number Sparking Coronavirus Fears
Here’s what the oft-cited R0 number tells us about the new outbreak—and what it doesn’t.
“When a new disease emerges, health organizations turn to a seemingly simple number to gauge whether the outbreak will spread. It’s called the basic reproduction number—R0, pronounced R-
nought—and though useful for decision makers, it’s a nightmare for public communication. In brief, R0 is the average number of people who will catch the disease from a single infected person, in a population that’s never seen the disease before. If R0 is 3, then
on average every case will create three new cases. But even though it seems incredibly straightforward, it’s hard to calculate and tricky to interpret.
R0 is important because if it’s greater than 1, the infection will probably keep spreading, and if it’s less than 1, the outbreak will likely peter out. So it offers vital information to organizations and nations as they consider how to respond to an outbreak—such as the one the world is currently experiencing.”
[...]
In the past week,
at least six teams ofresearchers, along with the
World Health Organization, have published estimates of R0 for the new coronavirus. All these groups used different methods, but their results have been mostly consistent, with estimates hovering between 2 and 3. WHO was a
little more conservativethan the others, with estimates of 1.4 to 2.5. One Chinese team is
a clear outlier, with estimates of 3.3 to 5.5. And a British-led group initially published a
high average value of 3.8 last week before revising it downward to 2.5 as new data emerged.
In the intervening time, however, some observers seized upon the 3.8 number, with one Harvard doctor describing it as “thermonuclear pandemic level bad” in a tweet that has since been
retweeted more than 16,000 times. That’s a dubious interpretation, and here are six reasons why.“
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