Monkeypox is caused by a virus that, despite periodic outbreaks, is not thought to spread easily from person to person and historically has not spurred long chains of transmission within communities. Now, many researchers are left scratching their heads as to why monkeypox seems to be propagating so readily and unconventionally in the current global outbreak.
The monkeypox virus typically spreads through direct contact with respiratory secretions, such as mucus or saliva, or skin lesions. Skin lesions traditionally appear soon after infection as a rash – small pimples or round papules on the face, hands or genitalia. These lesions may also appear inside the mouth, eyes and other parts of the body that produce mucus. They can last for several weeks and be a source of virus before they are fully healed. Other symptoms usually include fever, swollen lymph nodes, fatigue and headache.
I am an epidemiologist who studies emerging infectious diseases that cause outbreaks, epidemics and pandemics. Understanding what’s currently known about how monkeypox is transmitted and ways to protect yourself and others from infection can help reduce the spread of the virus.
The U.S. declared monkeypox a public health emergency on Aug. 4, 2022.
How is this outbreak different from prior ones?
The current monkeypox epidemic is a bit unusual in a few ways.
First, the sheer scope of the current epidemic, with over 25,000 cases worldwide as of early August and in countries where the virus has never appeared, sets it apart from previous outbreaks. Monkeypox is endemic to specific areas in central and western Africa, where cases occur sporadically and outbreaks are usually contained and quickly burn out. In the current outbreak, global spread has been rapid. Young men, mostly ages 18 to 44, account for the majority of cases, and over 97% identify as men who have sex with men (MSM). Some superspreading events associated with air travel, international gatherings and multiple-partner sexual encounters contributed to early transmission of the virus.
Second, the way symptoms are appearing may facilitate spread among people who don’t yet know they are infected. Most patients reported mild symptoms without fever or swollen lymph nodes, symptoms that typically appear before a skin rash is visible. While most people do develop skin lesions, many reported having only a single papule that was often obscured inside a mucosal area, such as inside the mouth, throat or rectum, making it easier to miss.
Monkeypox is not a new disease.
A number of people reported no symptoms at all. Asymptomatic infections are more likely to go undiagnosed and unreported than those with symptoms. But it is not yet known how asymptomatic individuals may be contributing to spread or how many asymptomatic cases may be undetected so far.