It's good news that the death rate from Covid-19 has trended dramatically downward since April, even as the number of new cases is surging. But it's far from the whole story.
Unlike common colds caused by other coronaviruses, Covid-19 is more than a transient, self-limited respiratory infection. There have been numerous reports of nonrespiratory manifestations, including loss of smell or taste, confusion and cognitive impairments, fainting, sudden muscle weakness or paralysis, seizures, ischemic strokes, kidney damage, abnormal blood-coagulation tests, transmission to an unborn child via the placenta, and a severe (though rare) pediatric inflammatory syndrome. Recovery is sometimes incomplete, with some patients experiencing long-term adverse effects that resemble a condition variously known as myalgic encephalomyelitis or chronic fatigue syndrome.
As the name suggests, CFS is group of symptoms that seem to define an illness, even if we don't know how they're related or what causes them. Signs and symptoms may include fatigue, loss of memory or concentration, sore throat, swelling of neck or armpit lymph nodes, unexplained muscle or joint pain, headaches, nonrestorative sleep and extreme exhaustion that lasts more than 24 hours after physical exercise or mental stimulation. People with CFS are often incapable of performing ordinary activities and sometimes become completely debilitated, unable to get out of bed. Manifestations of the syndrome can persist for years.
In recent decades, a range of long-term complaints resembling those of chronic fatigue syndrome have followed outbreaks of infectious diseases, including West Nile virus, H1N1 influenza, and Ebola, as well as Severe Acute Respiratory Syndrome and Middle East Respiratory Syndrome, both of which are also caused by coronaviruses. It's therefore no surprise to see similar complications in Covid-19 patients, though we don't know their long-term course.
The appearance of serious Covid-19 sequelae has important implications. First, fatalities aside, the increase in cases and the high numbers of hospitalizations in epicenters of infection can't be dismissed. We still need to suppress and mitigate Covid-19 aggressively. The fewer new cases, the fewer lingering illnesses there will be, with all their attendant misery and expense.
Second, the persistence of debilitating symptoms argues strongly against "human challenge trials" of vaccines, in which the infectious virus is intentionally administered to volunteers, some of whom would receive a trial vaccine while others get a placebo. In the absence of very effective drugs to treat Covid19, such studies would be unethical.
Finally, we need to anticipate and prepare for a wave of post-Covid illnesses with systematic research to understand better the pathophysiology of both the acute viral infection and its relationship to CFS and other sequelae. The sad truth is that we are still in the early days of this pandemic.
Dr. Miller, a physician and molecular biologist, is a senior fellow at the Pacific Research Institute. He was founding director of the Office of Biotechnology at the FDA.