How deadly is monkeypox?  What scientists know

How deadly is monkeypox? What scientists know

A nurse wearing protective gear stands at the entrance to an isolation ward for people with monkeypox.

Hospitals around the world treat people with monkeypox.Credit: Noah Seelam/AFP/Getty

The global outbreak of monkeypox has caused deaths, but the death rate is lower than expected based on historical data – and scientists breathe a cautious sigh of relief. Of more than 57,000 people confirmed to have had monkeypox infections, at least 22 have died, representing a fatality rate of approximately 0.04%. This is significantly lower than the 1-3% that has been reported in outbreaks caused by a similar viral strain in West Africa in recent decades.

All of this caused researchers to reevaluate what they thought they knew about severe monkeypox.

In reality, the true death rate is almost certainly higher than current estimates: countries in some parts of the world, including Africa, may not be recording all deaths during this outbreak because they have limited resources. for testing and monitoring. And it could rise further, especially if the virus spreads more widely among people at high risk of serious illness, such as children, the elderly and people with severely compromised immune systems, says Andrea McCollum, an epidemiologist who leads the poxvirus team in the United States. Centers for Disease Control and Prevention in Atlanta, Georgia.

Yet for the community that has been most affected so far – young and middle-aged men who have sex with men – the disease can be “extremely painful” and has “caused a lot of suffering”, says Jason Zucker, a contagious-disease physician at Columbia University in New York who has treated people with monkeypox. The pain comes from distinct fluid-filled lesions caused by the disease. Although some people have been hospitalized for life-threatening complications such as breathing difficulties or brain swelling, Zucker says, it’s more common to see people hospitalized for pain management.

In the current outbreak, clinicians have seen fewer lesions overall than in previous outbreaks in Africa. But a higher proportion of lesions appear on the mucous tissues of the body. Previously, lesions appeared mainly on the skin – on people’s hands, feet and faces. Mucosal damage is not inherently more serious, but it does aggravate sensitive tissue, so it can cause immense pain and interfere with swallowing, eating or drinking food or drink while in the throat, or urinating and defecating when they are in the genital and rectal areas, says Zucker.

These lesions are also more difficult to identify and characterize than skin lesions. That means the monkeypox severity scale recommended by the World Health Organization (WHO), which uses the number of lesions as an indicator of disease severity, might need some tweaking, McCollum says.

Serious results

So far, during the global epidemic, deaths from monkeypox have occurred in at least ten countries, including Brazil, India, Nigeria and Spain. Efforts are underway to understand how the virus contributed to these deaths.

Some of the people who died – including one in the United States and one in Mexico – were severely immunocompromised and suffered from serious illnesses other than monkeypox. (These deaths have not yet been recognized as monkeypox-related by the WHO.)

Two people who died in Spain developed encephalitis or brain swelling and had no other known risk factors. Based on previous monkeypox data, these deaths are “certainly alarming, but not entirely surprising,” McCollum says. Encephalitis is a rare but serious complication of many viral illnesses, including those caused by herpes simplex and West Nile virus, and has been known to occur in otherwise healthy people who are infected, says Zucker. It is still not known whether encephalitis due to monkeypox occurs as a result of infection of brain tissue with the virus or because of an excessive immune response that causes swelling of the brain.

Researchers have also observed seizures and encephalitis in people with monkeypox in previous outbreaks: a review of previous monkeypox literature published on September 8 found severe neurological symptoms in less than 3% of 1,512 people analyzed .1.

“We need to move beyond just thinking of monkeypox as a skin and respiratory disease,” says Jonathan Rogers, a neuropsychiatrist at University College London, who co-authored the analysis. The monkeypox virus may have evolved from past outbreaks, but scientists are also learning new things about it due to the larger and more geographically diverse population it now affects.

Who is most at risk?

More research is needed to understand which people are most at risk of developing severe monkeypox — and which routes of transmission might be the most dangerous, McCollum says. After a 2003 outbreak in the United States, when a shipment of rodents from Ghana spread the virus to pet prairie dogs in Illinois and infected more than 70 people, researchers noticed that the severity of illness differed. depending on the route of exposure.2. People scratched or bitten by infected animals tended to have more severe disease than people exposed to animal respiratory droplets and particles.

Although most infections in the current outbreak result from close sexual contact, McCollum says, the site of the body the virus first infects — skin versus mucosal tissue — could dictate the severity of illness.

More data is also needed to understand whether the effects of a severe case of monkeypox can persist after an infection clears up, Zucker says. In their analysis1, Rogers and his colleagues noticed that it is common to see scarring at the sites of old lesions. Not only could the scarring trigger stigma and depression, but it could also cause inflammation by constricting bodily channels such as the esophagus and colon, Zucker says.

“This reminds us that this is not a benign disease,” McCollum says. “It can be quite serious.”

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