Current messaging surrounding how monkeypox spreads is focused on sustained physical contact. But as the outbreak grows, with more than 6,000 cases now confirmed in the U.S., questions are also rising about whether and to what extent respiratory transmission plays a role.
According to the CDC, monkeypox is often spread via direct contact with infectious sores, scabs or body fluids, which often happens during intimate physical contact. The current outbreak supports that, with 98 percent of U.S. cases so far among men who have sex with men. The same is true for global cases, according to the World Health Organization.
As of Aug. 2, cases in the U.S. have surpassed 6,000, with health experts issuing warnings that the window is closing to contain the monkeypox outbreak and prevent the virus from becoming endemic. Experts have assured the public the virus doesn't transmit nearly as easily as COVID-19, with most reported monkeypox cases, again, involving close, sustained physical contact. But there appears to be at least some risk level regarding respiratory transmission.
The CDC does list contact with respiratory secretions as a method of transmission, but notes "scientists are still searching" for "how often" it's spread this way and when an infected, symptomatic person "might be more likely to spread the virus through respiratory secretions."
Ulcers, lesions or sores in the mouth can be infectious, "meaning the virus can spread through direct contact with the mouth, respiratory droplets and possibly through short-range aerosols," according to the WHO. "Possible mechanisms of transmission through the air for monkeypox are not yet well understood and studies are underway to learn more."
The bottom line is there is at least some level of transmission risk tied to respiratory secretions people should be aware of, said Robert Pitts, MD, an infectious disease specialist at New York City-based NYU Langone Health.
"These aren't secretions that are airborne for long periods of time," Dr. Pitts told Becker's. "They typically come into the air very shortly after they leave the person who is infected, and so in order for there to be that transmission with respiratory secretions, you have to have close, sustained contact with the person who's infected … I wouldn't consider it the highest risk of transmission, but something that we need to consider as we learn more about monkeypox."
There is also some evidence to support that the virus can be suspended in the air, according to a July study published ahead of peer review in medRXiv. The U.K. researchers conducted the study to inform infection prevention control measures after a U.K. healthcare worker was suspected to have contracted the virus while changing bedding. The study took place in U.K. healthcare facilities, and the researchers found the virus in air samples collected after bedding changes in isolation rooms used for infected patients, supporting the theory the virus may be present in suspended skin particles or dust.
"These data demonstrate significant contamination in isolation facilities and potential for aerosolization of [monkeypox virus] during specific activities," the study said.
Eric Feigl-Ding, PhD, an epidemiologist and former faculty member at Boston-based Harvard Medical School, has also raised concern about the potential for respiratory transmission. "It's not really true that it's 'not known to linger in the air,'" he wrote in a July 28 tweet, referencing the U.K. study and a CDC tweet that said monkepox is not known to linger in the air.
But even with early evidence suggesting the virus can become airborne in some capacity, it's not yet fully clear whether it can infect someone.
Like the early months of the COVID-19 pandemic, there have been discrepancies in the messaging surrounding how monkeypox spreads, leading to confusion among the public.
"This is very reminiscent of our experience with COVID, and I think we can all remember the discrepancies around wearing masks, the transmissibility of COVID, who was at risk, and I think … this all reminiscent of that," Dr. Pitts said.
"I think the messaging should just be clear that there is a [respiratory] risk and the risk is really maximized when you have sustained close contact with someone," Dr. Pitts said.