Hard numbers

It’s the middle of May. By the weekend, the death toll in Hudson County is likely to break the thousand mark. We count 16,975 cases. That’s a case fatality rate of 5.8%. Put another way: those with confirmed cases of the virus had a little better than a one in twenty chance of dying. If you’ve ever played Dungeons & Dragons, or another game that uses a d20 system, you know that rolling a natural twenty isn’t all that uncommon. Critical hit, double damage.

In neighboring counties, the numbers are worse. Essex, the next county over, and the heart of African-American New Jersey, has confirmed slightly fewer cases but considerably more deaths. Their current case fatality rate is almost ten percent. Bergen County isn’t far behind. As we know, many of those deaths have happened in nursing homes and long-term care facilities. But many of them have not. Some of those who didn’t make it already had serious medical issues. But many of them did not.

Initially, I thought that those percentages would decrease as the crisis developed. More testing plus more medication plus recovery and acquisition of antibodies seemed to point toward a better ratio of survivors to non-survivors. This hasn’t happened. Instead, I’ve watched the rate triple in eight weeks. Percentages have spiked on the other side of the Hudson, too. Even as more sick (and healthy) people have been checked, the grim numerator of mortalities has kept pace with the widening denominator of case confirmations.

Life during a public health crisis accustoms us to epidemiological language, and highlights some of our misconceptions. For instance, for weeks, I’ve been confusing case fatality rate with infection fatality rate, and that misunderstanding has skewed my apprehension of the dangers we face. We know that at least some — and possibly many — of the people infected with the coronavirus will remain asymptomatic. These people may never get tested, and may never even go to a doctor for a related complaint. They aren’t counted among the cases, and given current American priorities, it’s likely that they never will be.

Because of this, it’s been very difficult to calculate the infection fatality rate. Those who’ve tried to do it have been operating from incomplete information, and they’ve based their impressions on numbers from prior pandemics. That’s not a useless thing to do: precedent is important. It becomes dangerous, though, when the people doing the educated guesswork refuse to budge from their models. We all desperately want the case fatality rate to be low. Right now, though, we’re still listening to people who are absolutely determined to show that the casualty rates for this virus are equivalent to those associated with the flu. Some of this has been politically motivated — it’s tacit support for certain (mis)leaders who’ve pushed the line that this is just another kind of flu — and some of it is plain old wishcasting.

By now, you don’t have to be from New York or New Jersey to know that this is not just the flu. No flu has case fatality rates approaching ten per cent. Every year, there are thousands of cases of mild flu, too; people so afflicted don’t go to the doctor, either. We can better model infection fatality rates for the flu because we’ve had more than a century of experience with influenza. It was always a dicy thing to do to conflate the current outbreak with influenza, and anybody who is still doing it in May — anybody mentioning flu at all — is immediately suspect to me. The coronavirus is novel. It’s acting on us in ways that we still don’t understand. We ought to take the current case fatality rate seriously. We should stop reassuring ourselves that it’s going to be more palatable once the numbers are in. I fear it’s going to be awhile before numbers are friendly again.