In the past week, a virus other than SARS-CoV-2 has started making headlines. A monkeypox outbreak, first detected in the U.K. two weeks ago (the first case was reported on May 7), is causing concern among public health officials. Here is what we know so far.

One of the main reasons for alarm is the sharp increase in the number of reported cases. Moritz Kraemer, PhD, associate professor at the University of Oxford and the director of the Oxford Martin Program on pandemic genomics, is part of a group maintaining a running list of monkeypox cases reported around the world. In the afternoon of May 19, the tally was 75 (confirmed and suspected) cases across seven countries (England, Portugal, Spain, United States, Canada, Sweden, Italy). Later that night, the number had jumped to 107.

One case has been reported in the United States (in Massachusetts) and New York City is currently investigating a possible case.

Another cause for concern is that the virus is spreading from person to person. Although the first reported case had recently traveled to Nigeria, an area affected by monkeypox, many of the recently infected people had not traveled. This indicates human-to-human transmission within the community.

Perhaps the biggest question on everyone’s mind is how the virus is transmitted from person to person. And, how easily transmissible is it. Andrea McCollum, an epidemiologist in the CDC’s Poxvirus and Rabies Branch told STAT that the virus is transmitted through contact with a patient’s lesions and/or materials that contact the lesions—like clothes and bed linens. It is presumed that the virus spreads through respiratory droplets as well, McCollum estimates, due to lesions in the mouth.

Marion Koopmans, DVM, PhD, head of the Erasmus MC department of viroscience, tweeted that the outbreak is “starting to be worrisome,” because the cases are in different countries. This is unusual, she said, because “monkeypox is not that contagious.”

Monkeypox and smallpox 

Monkeypox is in the orthopoxvirus genus—the same genus that includes variola virus, the causative agent of smallpox.

The last natural outbreak of smallpox in the United States was in 1949. The last cases in the world were in the late 1970s. And, smallpox was declared eradicated during the 33rd World Health Assembly on May 8, 1980.

Monkeypox was first discovered in 1958 when two outbreaks of a pox-like disease occurred in colonies of monkeys kept for research. The first human case of monkeypox was recorded in 1970 in the Democratic Republic of the Congo.

Because of the similarity in the viruses, the smallpox vaccine should have cross-protection against monkeypox. Some data suggest that the smallpox vaccine is at least 85% effective in preventing monkeypox.

Indeed, the mobilization of smallpox vaccines has already started.

The Denmark-based vaccine company Bavarian Nordic announced on May 18, that the U.S. Biomedical Advanced Research and Development Authority (BARDA) has exercised the first options under a contract to manufacture doses of the Jynneos smallpox vaccine. This will allow the first doses of this version to be manufactured and invoiced in 2023 and 2024.

Experts may not have all of the answers yet. But they seem to agree that the number of cases, and countries reporting monkeypox cases, is bound to increase.

Bill Hanage, PhD, associate professor at Harvard T. H. Chan School of Public Health, tweeted that “the clusters of monkeypox infections that are turning up should be treated with the utmost seriousness.”

The basics

Symptoms: Monkeypox begins with fever, headache, muscle aches, backache, swollen lymph nodes, chills, and exhaustion.

Within days after the appearance of fever, the patient develops a rash, often beginning on the face, then spreading to other parts of the body.

The lesions progress through the following stages before falling off: macules, papules, vesicles, pustules, scabs.

The illness typically lasts for 2−4 weeks.

Incubation period:  The incubation period (time from infection to symptoms) for monkeypox is usually 7−14 days but can range from 5−21 days.

Mortality rate: Monkeypox has been reported to cause death in as many as 10% who contract the disease, in Africa.

Natural reservoir: Unknown.

Reference: CDC.gov