The CDC expects that samples from four other people in the United States will test positive for monkeypox virus, which would bring the U.S. total to five cases amid a widening outbreak of the disease in countries where it is not endemic.

Jennifer McQuiston, DVM, MS, deputy director of the CDC’s Division of High Consequence Pathogens and Pathology, said in a telebriefing Monday that four more men in the U.S. have tested positive for orthopoxvirus, a genus of viruses that includes monkeypox.

Although states can test patients for orthopoxviruses, confirmatory testing for monkeypox must be done at the CDC, McQuiston explained. She said the CDC presumes that all four men — two in Utah and one each in New York City and Florida — have monkeypox.

“It’s likely that there are going to be additional cases reported in the United States,” McQuiston said.

The CDC last week confirmed a case of monkeypox in a Massachusetts man who had traveled to the U.S. from Canada. In fact, all five confirmed and presumed U.S. cases have involved travel, McQuiston said — although there have been nontravel-related cases in the wider outbreak, which is unusual for monkeypox outside of endemic countries, officials have said.

Canada, Australia and numerous countries in Europe have also reported cases in the current outbreak — most of them mild.

The cases have mostly involved — but are not limited to — men who have sex with men (MSM). The European Centre for Disease Prevention and Control said Monday that a predominance of cases occurring among MSM “and the nature of the presenting lesions in some cases, suggest transmission occurred during sexual intercourse.”

“Anyone can develop and spread monkeypox infection but many of those infected by the current monkeypox outbreak identify as gay or bisexual men,” John Brooks, MD, a medical epidemiologist in the CDC’s Division of HIV/AIDS Prevention, said during the briefing Monday.

“Monkeypox is not a sexually transmitted infection in the typical sense, but it can be transmitted during sexual and intimate contact, as well as personal contact through shared bedding or clothing,” Brooks said.

Brooks said anyone with a new or unexplained rash or symptoms should tell their doctor or otherwise seek medical attention. He said the CDC would provide clinicians with information on what monkeypox looks like and how to manage it.

“In some cases, during the early stages, the rash has been mostly in the genital region and that could look like other diseases,” Brooks said.

Monkeypox is rare outside of the handful of African countries where it is endemic, which include Nigeria and the Democratic Republic of the Congo (DRC). There were two reported cases in the U.S. last year — both linked to travel from Nigeria, where an outbreak that has been ongoing for years has shown evidence of human-to-human transmission.

A 2003 outbreak in the U.S. that involved dozens of people was related to exposure to imported prairie dogs that had contact with infected rodents, which are suspected of being the natural reservoir for the virus, despite its name.

McQuiston said the CDC was able to quickly sequence a sample from the Massachusetts case and that it closely matched sequencing from Portugal.

Recent cases in the U.S. and Europe have been associated with the West African clade of monkeypox virus, which is historically less deadly than the Congo Basin clade — a 3.6% vs. 10.6% case fatality rate, according to WHO.

Some countries in Africa have reported dozens of cases of monkeypox this year. The DRC has reported more than 1,200 cases, according to WHO.

Researchers who reviewed cases of monkeypox going back to the 1970s — when the disease was first reported in humans — said waning population immunity against smallpox has left the world more vulnerable to outbreaks of monkeypox.

Smallpox vaccination provides some cross-protection against monkeypox, but countries have not routinely vaccinated against smallpox since the disease was declared eradicated in 1980. (The U.S. halted routine smallpox vaccination in 1972.)

A two-dose vaccine that protects against both monkeypox and smallpox — Bavarian Nordic’s Jynneos — was approved by the FDA in 2019 for adults and is kept in the U.S. Strategic National Stockpile. There are more than 1,000 doses available in the U.S., with more expected to be delivered over the coming weeks, McQuiston said. There are around 100 million available doses of a second smallpox vaccine, but it has some potential serious side effects and any decision to use it “would have to have some serious discussion behind it,” McQuiston said.

“Right now, we are hoping to maximize vaccine distribution [of the Bavarian Nordic vaccine] to those that we know would benefit from it,” McQuiston said. “So, those are people who’ve had contact with a known monkeypox patient — health care workers, very close personal contacts, and those in particular who might be at high risk for severe disease.”

References:

The European Centre for Disease Prevention and Control. Risk assessment: Monkeypox multi-country outbreak. https://www.ecdc.europa.eu/en/publications-data/risk-assessment-monkeypox-multi-country-outbreak. Published May 23, 2022. Accessed May 23, 2022.

WHO. Monkeypox. https://www.who.int/news-room/fact-sheets/detail/monkeypox. Accessed May 23, 2022.

WHO. Multi-country monkeypox outbreak in non-endemic countries. https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON385. Published May 21, 2022. Accessed May 23, 2022.

PERSPECTIVE

 

Amira A. Roess, PhD, MPH

We’ve dealt with numerous monkeypox outbreaks over the last few decades since monkeypox virus was first identified. Monkeypox outbreaks tend to burn themselves out, and historically that was due to the limited chain of transmission from the point of the spillover event to the close contacts of the first human case. However, increased encroachment into wildlife areas, combined with rapid urbanization and globalization, mean that we will see elongated chains of transmission, as we appear to be seeing now.

In addition, the immunity many people had as a result of the smallpox vaccination campaign has waned considerably because the last case was more than 40 years ago and global vaccination was discontinued following the successful eradication of smallpox. Another harsh reality is that in many countries, we have a large percentage of adults who are immunocompromised and susceptible to severe illness from infectious diseases, including monkeypox. Before the COVID-19 pandemic, those on immunosuppressive medications or who are otherwise immunocompromised lived with the fear of influenza, cold, and other infections. This was and is a reality. What’s changed is that we have many more individuals who can be considered high risk for severe illness from infectious diseases, and that number will continue to increase as we get better at treating cancer and other illnesses and as people live longer.

Smallpox is a virus related to monkeypox. Governments and global leaders are well aware of the global pandemic fatigue and are hesitant to impose similar measures to control monkeypox as they did SARS-CoV-2. Our previous experience suggests that because monkeypox is less transmissible than SARS-CoV-2, it will not be necessary to impose stay-at-home orders or restrict movement at the scale that we have seen. What can change all of this is if we find that this is a new strain that transmits more rapidly than previous ones or if we find that it is a more virulent strain than previously.

Amira A. Roess, PhD, MPH

Professor of global health and epidemiology

George Mason University