Greater public health response needed to limit monkeypox’s evolution, experts say

Colorized transmission electron micrograph of monkeypox virus particles
Colorized transmission electron micrograph of monkeypox virus particles (yellow) cultivated and purified from cell culture. Image captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Credit: NIAID

Waiting to put into place aggressive public health measures until monkeypox virus cases are higher could actually speed the virus’ evolutionary development and adaptability in humans, write a group of infectious disease scientists in a correspondence published Wednesday in The Lancet.

“We have a perfect setup for monkeypox to establish itself in the human population outside of Africa unless we are much more aggressive in our intervention strategies,” said Ira Longini, Ph.D., one of the authors and a professor of biostatistics in the University of Florida College of Public Health and Health Professions and College of Medicine.

Currently, monkeypox’s reproductive number, or the average number of people infected by one individual, is slightly greater than 1. And while that contagion rate seems low compared to some recent COVID-19 variants, for example, the experts say it represents a higher probability of viral evolution. The longer the virus is circulating before cases reach a point when authorities act, the greater the opportunity the virus has to acquire mutations, the authors write.

“For a given number of cases you observe in a particular point in time, the smaller the basic reproductive number means the more cases that got you to that point,” said Longini, a member of UF’s Emerging Pathogens Institute. “In other words, the chains of transmission are much longer, which gives a lot more opportunity for evolution.”

With the discontinuation of smallpox vaccinations in much of the world following the disease’s elimination in the early ’70s, many populations do not have cross-immunity against pox viruses, which may also allow monkeypox to gain a foothold in younger groups, Longini said. Smallpox was declared eradicated in 1980.

Longini, who serves as an advisor to the World Health Organization on monkeypox vaccine evaluation, recommends implementing behavior modification strategies and contact tracing programs to limit exposure among at-risk groups. Vaccination campaigns using a ring vaccination strategy that targets close contacts of people who become infected could contain outbreak clusters.

While monkeypox case numbers are starting to decline in some parts of the world, including the U.S. and Europe, they are on the rise in other areas, such as Latin America.

“Just because transmission is going down in certain parts of the world, does not mean we are out of the woods,” Longini said. “Lowered transmission due to behavior changes and vaccination is encouraging and we can be hopeful, but that doesn’t necessarily eliminate the problem of further evolution of the virus.”

–Jill Pease