The window to contain the global monkeypox outbreak may be narrowing, with World Health Organisation Director-General Tedros Adhanom Ghebreyesus warning: “The risk of monkeypox becoming established in non-endemic countries is real.”
“As you keep moving forward into the future and more and more individuals become infected, you do start to worry,” George Mason University professor of global health and epidemiology Amira Albert Roess said.
“There’s still a window of opportunity to prevent the onward spread of monkeypox in those at highest risk right now,” WHO’s technical lead on monkeypox, Dr Rosamund Lewis, said at a briefing in Geneva.
Two smallpox vaccines may be key to the prevention effort. The US government’s preferred shot, called Jynneos, is specifically approved for use against monkeypox.
“This is one of the rare diseases in which you can vaccinate somebody after they’ve been infected, before they have symptoms, and block the disease,” Johns Hopkins Centre for Health Security senior scholar Eric Toner said.
The largest outbreak in the western hemisphere before now was a cluster of 47 cases in the US in 2003. However, there was no documented person-to-person transmission – everyone infected had been in contact with sick prairie dogs.
In the current outbreak, the primary driver of transmission seems to be skin-to-skin contact between people, often involving exposure to infected people’s rashes or lesions.
“Right now we’re more at risk for the virus maybe becoming endemic due to ongoing human-to-human transmission and our inability to stop the transmission cycle,” Roess said.
Several factors are involved in that cycle. For one, some monkeypox cases are hard to identify. Patients develop rashes that can be confused with chickenpox, syphilis or herpes but in some cases it may be limited to the genital area, making it harder to detect.
University of Pennsylvania associate professor of medicine Dr Stuart Isaacs said the virus could have “epidemic potential” in the US — meaning there would be a major surge in cases — if a single infected person spread monkeypox to more than one other person on average. That hasn’t been the case in the past, and the US has recorded fewer than 40 cases thus far.
“The reason this is endemic in Africa is there’s animal reservoirs,” he added. “The virus is propagating and spreading among animals, and then it jumps into humans or non-human primates every now and then.”
In the past, Roess said, countries outside Africa quickly halted monkeypox outbreaks through testing and contact tracing, but the current outbreak is unprecedentedly large and widespread.
Experts don’t yet know whether its scale is a clue that monkeypox has evolved to get better at human-to-human transmission or whether countries are simply uncovering the extent of an outbreak that went undetected for some time.
Already, the monkeypox outbreak may meet the formal definition of a pandemic: The virus is spreading from person to person in at least two countries, and there are community-level outbreaks in several parts of the world.
“But generally, when we talk about pandemics, we talk about diseases in which everyone is significantly at risk in every country or almost every country,” Toner said. “So far, this has not reached that threshold, and I don’t think it ever will.”
A reason for optimism, however, is that this version of monkeypox isn’t usually life-threatening. Although monkeypox rashes can be painful and cause scarring, experts said, doctors know how to treat them with smallpox antivirals and supportive care. No deaths have been reported in non-endemic countries thus far.