Do Omicron numbers mean what we think they mean?

There’s an urban legend about a man in Texas who grabs a gun from the side of his barn and sprays bullets at the wall, more or less at random. Then it finds the densest clusters of holes and paints a bullseye around each one. Later, a passer-by, impressed by this parade, trots in search of the shooter. In a reversal of cause and effect, the Texas Sharpshooter was born.

The sniper fallacy is often used by scientists to illustrate our tendency to narrativize data after the fact. We can observe an unusual clustering of cancer cases and come back to an explanation, choosing statistics and ignoring the vagaries of chance. As we cross covidWinter surge of -19, the story holds a deeper lesson about the perils of interpreting data without a full appreciation of the context. Omicron, due to its extraordinary contagiousness and relative mildness, has transformed the risks and consequences of infection, but not our reading of the statistics that have guided us through the pandemic. Do numbers always mean what we think they mean?

A coronavirus infection is not what it used to be. Studies suggest that, compared to Delta, Omicron is three to two times less likely to send someone to the hospital; by some estimates, the risk of an older, vaccinated person dying from covid is now lower than the risk posed by seasonal influenza. And yet, the variant exacts a heavy toll – medical, social, economic. (Omicron still poses a major threat to unvaccinated people.) The United States is seeing, on average, more than eight hundred thousand coronavirus cases per day, three times the peak of last winter. Given the growing use of home testing, this official tally greatly underestimates the true number of infections. We don’t know how many rapid tests are used each day, or what proportion are positive, making traditional measures unreliable, such as a community’s test positivity rate, which is used to guide policy on everything , from school closures to sporting events.

There are many other numbers we would like to know. How likely is Omicron to deliver you not an irritating cold but the worst flu of your life? How does this risk increase with the number and severity of health problems a person has? What are the chances of persistent symptoms following a mild illness? How long does immunity last after a booster or infection? Americans don’t wait to find out. Last week, social distancing and self-quarantine rates hit their highest level in nearly a year, and restaurants, shops and social gatherings fell to new lows. Half of Americans believe it will take at least a year to return to their pre-pandemic lives, if they ever do; three-quarters believe they are as or more likely to contract the virus today – a year after vaccines became available – as they were at the start of the pandemic.

Should we focus only on the number of cases? Some experts, including Anthony Fauci, argue that hospitalizations are now the most relevant marker of viral damage. More than one hundred and fifty thousand Americans are currently hospitalized with the coronavirus, a higher number than at any other time during the pandemic. But that number, too, is not quite what it seems. Many hospitalized covid patients have no respiratory symptoms; they were admitted for other reasons – heart attack, hip fracture, cancer surgery – and tested positive for the virus. There are no nationwide estimates of the proportion of patients hospitalized with covid”, but in New York State, about forty percent of patients hospitalized with covid It is believed that they were admitted for other reasons. The Los Angeles County Department of Health Services reported that accidental infections accounted for about two-thirds of covid admissions to its hospitals. (Pediatric covid hospitalizations have also reached record highs, probably because the transmissibility of Omicron means that many more children contract the virus; however, there is little evidence that the variant causes them more severe disease.)

Clarifying the distinction between a virus that fuels disease and one that just gets in the way is more than an academic exercise. If we count asymptomatic or minimally symptomatic infections as covid hospitalizations, we risk exaggerating the toll of the virus, with all the social and economic ramifications that follow. If we exaggerate the degree of accident covid, we risk promoting an erroneous sense of security. Currently, the United States does not have data collection practices or a unified framework for separating one type of hospitalization from another. To complicate all this, it is sometimes difficult to distinguish a person hospitalized “with covid“of a hospitalized” for covid.” For some patients, a coronavirus infection can worsen a seemingly unrelated condition – a covid fever drives an elderly woman with a urinary tract infection into delirium; an attack of diarrhea dehydrates a man admitted for sickle cell disease. In such cases, covid is not an innocent bystander, nor does he start the fire – he adds just enough tinder to push a manageable issue into a crisis.

It is a positive development that we can engage in this discussion. With Alpha and Delta, almost all covid hospitalizations were related to infection. The situation is different with Omicron, due to both its reduced ability to replicate in the lungs and its greater ability to infect people who have been vaccinated or have already contracted the virus. Yet analyzing the numbers in a moment of crisis may seem like a secondary objective. Omicron places an undeniable strain on the healthcare system. Last week, a quarter of US hospitals reported critical staffing shortages. Many have postponed non-emergency surgeries and some have asked their employees to continue working even after being infected. Some states have called in the National Guard; others have adopted “crisis care standards,” under which overwhelmed hospitals can restrict or deny treatment to certain patients – intensive care beds, ventilators and other vital resources – in order to prioritize those who are the most vulnerable. more likely to benefit.

But this wave will also pass, perhaps soon. In the end, the vast majority of Americans might have some degree of immunity, resulting from vaccination, infection, or both. In all likelihood, we would then be approaching the endemic phase of the virus and be left with a complex set of questions about how to live with it. What level of disease are we willing to accept? What is the purpose of new restrictions? What do we owe each other? A lucid view of the numbers will illuminate the answers. But it’s up to us to paint the targets. ♦