An Explanation for Some Covid-19 Deaths May Not Be Holding Up

Medical researchers are raising significant doubts about whether an agent of the human immune system causes some coronavirus patients to end up in the hospital with injured lungs and other organs, struggling to breathe. What remains is a continuing mystery about what causes certain people to die from Covid-19, and how best to prevent that.

A hypothesis that emerged early in the pandemic involves cytokine storms, an immune system response that is often invoked to explain severe viral infections, and to many doctors it seemed to make perfect sense: Patients who died from Covid were found to sometimes have little or no virus in their bodies. Their immune systems got rid of it. But in doing so, the hypothesis went, their body’s defenses went rogue, spewing out powerful compounds — cytokines and other drivers of inflammation — that fatally damaged tissues and organs in a storm.

But in a number of recent studies, some researchers say, an agent suspected of causing the storms might not be the culprit or that such storms might not happen in the way doctors believed.

Not everyone agrees.

Dr. Randy Cron, a professor of pediatrics and medicine at the University of Alabama at Birmingham who has long studied cytokine storms, says some hospitalized Covid-19 patients do experience these immune overreactions. But he agrees they are not identical to the reactions seen in other disorders, and much remains to be learned.

The storm idea has so far centered on one cytokine, interleukin-6, or il-6. The belief that it might be the culprit in certain Covid deaths began with reports from China early in the course of the pandemic. Doctors there said a patient who fared poorly had high levels of il-6. The doctors tried using drugs that block il-6, and the patient recovered. Similar reports followed there and in Italy. ...