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 volume of cases as a pandemic.
But could that change? Given its spread, it could monkeypox become a pandemic?
The answer to this question depends on the definition of “pandemic”. A pandemic is a “global 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.
“I think it’s a matter of opinion 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, will change, but several factors reduce the chances of monkeypox becoming a pandemic. Even if that happens, monkeypox won’t come close to accounting for 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 monkeypox transmission was short — a case of MPXV transmitted to about seven people at most before it died, so outbreaks have been short-lived in the past, Roper said. Monkeypox was first documented infecting humans in 1970, and cases since then, excluding the current pandemic, have been “kind of small,” he said. In countries where it is endemic, monkeypox is always present in animal hosts and usually spreads between humans only when animals catch it and start transmitting it to other humans.
But an analysis of monkeypox genomes from the current outbreak, published June 24 in the journal Nature Medicine (opens in new tab)suggests that the version of the virus currently circulating has been passing from person to person with an unbroken chain of transmission since 2017. This indicates that the average chain of transmission is increasing, Roper said.
However, for monkeypox, the reproductive number (R0), or the number of individuals directly infected by each individual with the disease, has historically been less than 1, meaning that any outbreak would eventually die out even without active control measures of the disease (In contrast, the R0 for currently circulating microbial 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 a Document June 2022 (opens in new tab) in The Lancet Infectious Diseases journal.
It’s hard to say why monkeypox is infecting so many people now, he added. It could be because mutations have made it more contagious, or it could be because it has entered new populations that altogether have different behaviors or risk factors that increase transmission rates, Roper said.
For example, in African countries where monkeypox is endemic, the virus was not previously known to spread through men having sex with men, Roper said. However, the current epidemic mainly affects men who have sex with men and is spread through sexual and other intimate physical contact, according to World Health Organisation (opens in new tab) (WHO).
Monkeypox mutates quite slowly
Monkeypox is a virus that consists of DNA, as opposed to being composed of single-stranded ribonucleic acid (RNA). This matters because DNA replication involves fewer errors than RNA replication, so monkeypox mutates more slowly than counterparts like SARS-CoV-2 or HIV. This gives monkeypox viruses less opportunity to evolve to become more contagious than RNA viruses, according to the American Society for Microbiology (opens in new tab).
However, for a smallpox virus, monkeypox develops mutations quickly, according to the June Nature Medicine genome analysis. Compared to strains circulating in 2018 and 2019, the virus currently circulating has 50 mutations, likely picked up while circulating in humans, according to the paper. That’s six to 12 times the number of mutations expected based on the typical mutation rate for smallpox viruses, the paper’s authors noted.
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 spreads when an infected person sneezes, coughs or even just breathes, Roper said. In contrast, monkeypox is spread primarily by “direct contact with a rash, scab, or body 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.
“Monkey pox is so inefficient in the way it spreads,” Rodney Rohde, professor and chair of clinical laboratory sciences at the University of Texas, told Live Science. “You have to be very close, in skin-to-skin contact, or maybe with fomites like bedding or clothing. And it actually takes a long time, so many hours of contact, for that to happen, whereas [for] an aerosolized virus, it can be instantaneous – someone sneezes or coughs in a room and you inhale it and maybe 8, 10, 12 people get it.”
We already have vaccines and treatments for monkeypox
Two vaccines, JYNNEOS and ACAM2000, have been approved for use against monkeypox in the US, as Live Science was mentioned earlier.
While there are no specific treatments for monkeypox, according to the CDC (opens in new tab)antiviral drugs developed to combat blessingsuch as tecovirimat (TPOXX), may be recommended for people with weakness immune systems.
Given the availability of vaccines and treatments, combined with other factors such as the low fatality rate of the monkeypox strain currently circulating, it should be possible to slow the rate of infection and limit deaths, Rohde said. The fatality rate for the type of monkeypox circulating in the current outbreak has historically been about 1%, according to CDC (opens in new tab). But the current outbreak may be far less deadly. based on WHO numbers from late September, the fatality rate is 0.04%. While these numbers are still a rough estimate, they suggest that the monkeypox toll is likely to be much, much lower than that of COVID-19, even if monkeypox becomes a pandemic. “It could be considered a pandemic at some point because of the number of countries that have cases and the kind of linear increase in cases that we’re seeing,” Rode said. “But I don’t think it’s going to be the kind of global mortality crisis we saw with COVID.”
Originally published in Live Science.