As of September 21, the current monkeypox outbreak has infected 62,532 people in 105 countries. However, the World Health Organization (WHO) has not yet classified the current number of cases as a pandemic.
But can that change? Given its prevalence, it might monkeypox become a pandemic?
The answer to this question depends on the definition of “pandemic”. The pandemic is a “worldwide epidemic” in which there are large numbers of cases or outbreaks in many countries, Rachel Roper, a professor of microbiology and immunology at East Carolina University in Greenville, North Carolina, told Live Science in an email.
“I think it’s a matter of opinion exactly how many cases you should have in how many countries,” Roper said. The Centers for Disease Control and Prevention (opens in new tab) (CDC) defines a pandemic as “a disease event in which there are more cases of disease than expected, spread over several countries or continents, usually involving person-to-person transmission, and affecting large numbers of people.”
There is always a chance that something, such as the genetic code of the virus, can change, but several factors reduce the chances of monkeypox becoming a pandemic. Even if it did, monkeypox would not take anywhere near the toll of the COVID-19 pandemic, experts told Live Science.
Historically, monkeypox was not terribly contagious and outbreaks were small
Monkeypox (sometimes abbreviated as MPXV or MPX) “is much less contagious than COVID,” Roper said. Typically, the chain of transmission of monkeypox is short — one case of MPXV is transmitted to about seven people at most before it disappears — so outbreaks have been short-lived in the past, Roper said. Monkeypox was first documented to infect humans in 1970, and outbreaks since then, except for the current pandemic, have been “kind of small,” she said. In countries where it is endemic, monkeypox is always present in animal hosts and usually only spreads to humans when they catch it from animals and start passing it on to other people.
But an analysis of monkeypox genomes from the current outbreak, published June 24 in the journal Natural medicine (opens in new tab)suggests that the version of the virus currently circulating has been passing from person to person in an unbroken chain of transmission since 2017. This indicates that the average transmission chain is increasing, Roper said.
Yet, for monkeypox, the reproduction number (R0), or the number of people directly infected by each person with the disease, has historically been less than 1, meaning that any outbreak will eventually die out even without active measures to control the disease (In contrast, the R0 for currently circulating omicron variants of SARS-CoV-2, the virus that causes COVID-19, is estimated to be between six and 10, according to The conversation (opens in new tab).) But researchers don’t know the R0 for the version of monkeypox currently circulating, according to Document dated June 2022 (opens in new tab) in the journal The Lancet Infectious Diseases.
It’s hard to say why monkeypox is infecting so many people now, she added. It could be because mutations have made it more transmissible, or it could be because it has entered new populations that generally have different behaviors or risk factors that increase transmission rates, he said. Roper.
For example, in African countries where monkeypox is endemic, the virus has not been known to spread through men who have sex with men, Roper said. But the current epidemic mostly affects men who have sex with men and is spread through sexual and other close physical contact, according to World Health Organization (opens in new tab) (WHO).
Monkeypox mutates quite slowly
Monkeypox is a virus made by DNA, as opposed to single-stranded ribonucleic acid (RNA) composition. This matters because DNA replication involves fewer errors than RNA copying, so monkeypox mutates more slowly than counterparts like SARS-CoV-2 or HIV. According to American Society for Microbiology (opens in new tab).
Still, for a poxvirus, monkeypox evolves mutations quickly, according to a genome analysis in Nature Medicine in June. Compared to strains circulating in 2018 and 2019, the currently circulating virus has 50 mutations, most likely picked up while circulating in humans, according to the report. This is six to 12 times the number of mutations expected based on the typical mutation rate for poxviruses, the paper’s authors note.
It’s not a lung virus
The virus that causes COVID-19 is “predominantly respiratory,” Roper said. “Its main target organ is the lungs.” SARS-CoV-2 is spread when an infected person sneezes, coughs or even simply breathes, Roper said. In contrast, monkeypox is spread primarily through “direct contact with a monkeypox rash, scabs, or bodily fluids from a person with monkeypox,” according to the Centers for Disease Control and Prevention (CDC). The virus can also be spread when a person touches objects and surfaces that have been used by someone infected with monkeypox.
“Monkeypox is so inefficient in terms of how it spreads,” Rodney Rohde, professor and chair of the Texas State University Clinical Laboratory, told Live Science. “You have to be very close, skin-to-skin contact or maybe with fomites like bedding or clothing. And it actually takes a long time, so several hours of contact to happen until [for] an aerosolized virus, it can be instantaneous—someone sneezes or coughs in the room and you breathe it in and maybe 8, 10, 12 people get it.”
We now have vaccines and treatments for monkeypox
Two vaccines, JYNNEOS and ACAM2000, are approved for use against monkeypox in the US, as Live Science reported earlier.
Although there is no treatment specifically for monkeypox, according to CDC (opens in new tab)antiviral drugs that have been developed to fight smallpoxsuch as tecoxiramit (TPOXX), may be recommended for people with debilitated immune systems.
Given the existence of vaccines and treatments, combined with other factors, such as the low death rate of the monkeypox strain currently circulating, it should be possible to slow the rate of infection and limit deaths, Rode said. The mortality rate for the type of monkeypox circulating in the current outbreak has historically been around 1%, according to CDC (opens in new tab). But the current outbreak may be far less deadly; based on WHO data from the end of September, the death rate is 0.04%. While these numbers are still a rough estimate, they suggest that monkeypox casualties are likely to be much, much lower than those from COVID-19, even if monkeypox becomes a pandemic. “This could be considered a pandemic at some point because of the number of countries where there are cases and the kind of linear increase in cases that we’re seeing,” Rode said. “But I don’t believe it will be the type of global mortality crisis we saw with COVID.”
Originally published on Live Science.