As of September 21, the current monkeypox outbreak has infected 62,532 people in 105 countries. Still, the World Health Organization (WHO) has not yet classified the current number of cases as a pandemic.
But could that change? Given its spread, could monkey pox become a pandemic?
The answer to that question depends on the definition of “pandemic.” A 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 LiveScience. com in an email.
“I think it’s a matter of opinion how many cases you have to have in how many countries,” Roper said. the Centers for Disease Control and Prevention (opens in a new tab) The CDC defines a pandemic as “a disease event in which there are more cases of a disease than expected that are spread across multiple countries or continents, usually involving person-to-person transmission and affecting large numbers of people.”
There is always the chance that something, like the genetic code of the virus, could change, but several factors reduce the chances of monkeypox becoming a pandemic. Even if it does, monkeypox won’t come close to the toll of the COVID-19 pandemic, experts told LiveScience.
Historically, monkeypox hasn’t been terribly contagious and outbreaks have been small.
Monkeypox (sometimes abbreviated as MPXV or MPX) “is much less contagious than COVID,” Roper said. Monkeypox’s chain of transmission was typically short: A case of MPXV would spread to about seven people at most before disappearing, so outbreaks have been short-lived in the past, Roper said. Monkeypox was first documented as infecting humans in 1970, and outbreaks since then, excluding the current pandemic, have been “a little small,” he said. In countries where it is endemic, monkeypox is always present in animal hosts and usually spreads among humans only when they catch it from animals and start transmitting it to other people.
But an analysis of monkeypox genomes from the current epidemic, published June 24 in the journal Natural medicine (opens in a new tab)it suggests that the currently circulating version of the virus has been passing from human to human in an unbroken chain of transmission since 2017. This indicates that the average chain of transmission is increasing, Roper said.
Still, for monkeypox, the reproductive number (R0), or the number of people directly infected by each person with the disease, has historically been less than 1, meaning that any epidemic would eventually end even without active prevention measures. disease control (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, based on The conversation (opens in a new tab).) But researchers don’t know the R0 of the currently circulating version of monkeypox, according to a June 2022 document (opens in a new tab) in The Lancet Infectious Diseases.
It’s hard to say why monkeypox is infecting so many people now, he added. It may be because mutations have made it more transmissible, or it may be because it has entered new populations that collectively 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 who have sex with men, Roper said. But the current outbreak primarily affects men who have sex with men and is spread through close sexual and physical contact, according to the World Health Organization (opens in a new tab) (WHO).
Monkeypox mutates very slowly
Monkeypox is a virus made of DNA, as opposed to being composed of single-stranded ribonucleic acid (RNA). This is important because DNA replication involves fewer errors than RNA copying, so monkeypox mutates more slowly than its counterparts such as SARS-CoV-2 or HIV. This gives monkeypox viruses less opportunity to evolve to become more transmissible than RNA viruses, according to American Society for Microbiology (opens in a new tab).
Still, for a poxvirus, monkeypox is mutating rapidly, according to analysis of the genome in June Nature Medicine. Compared to the strains that circulated in 2018 and 2019, the currently circulating virus has 50 mutations, most likely detected while circulating in humans, according to the article. That’s six to 12 times the number of mutations expected based on the typical mutation rate of poxviruses, the paper’s authors noted.
It is not a lung virus
The virus that causes COVID-19 is “primarily respiratory,” Roper said. “Its main target organ is the lungs.” SARS-CoV-2 spreads when an infected person sneezes, coughs or just breathes, Roper said. In contrast, monkeypox is spread primarily by “direct contact with the monkeypox rash, scabs, or body fluids of 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 the way it spreads,” Rodney Rohde, professor and chair of clinical laboratory sciences at Texas State University, told Live Science. “You have to be very close, skin-to-skin contact, or maybe fomites like bedding or clothing. And it actually takes a long time, several hours of contact, for it to happen, whereas [for] an aerosol virus, it could be instant: someone sneezes or coughs in a room and you breathe it in, and maybe 8, 10, 12 people get it.”
We already have vaccines and treatments for monkeypox
Two vaccines, JYNNEOS and ACAM2000, are approved for use against monkeypox in the US, as Live Science previously reported.
Although there are no specific treatments for monkeypox, according to the Centers for Disease Control and Prevention (opens in a new tab)antiviral drugs that were developed to combat smallpoxsuch as tecovirimat (TPOXX), may be recommended for people with debilitating immune system.
Given the existence of vaccines and treatments, combined with other factors, such as the low mortality rate of the currently circulating strain of monkeypox, it should be possible to reduce the rate of infection and limit deaths, Rohde said. The mortality rate from the type of monkeypox circulating in the current epidemic has historically been around 1%, according to the Centers for Disease Control and Prevention (opens in a new tab). But the current outbreak may be much less deadly; according to WHO figures from the end of September, the mortality rate is 0.04%. While those numbers are still a rough estimate, they suggest the death toll from monkeypox 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 linear increase in cases that we’re seeing,” Rohde said. “But I don’t think it’s the kind of global mortality crisis that we saw with COVID.”
Originally published on Live Science.