This year has seen an unprecedented outbreak of monkeypox sweeping across the globe, and the disease appears to be “behaving differently” from before, experts told Newsweek.
Monkeypox is a rare, viral disease that has traditionally been confined to endemic areas in central and west Africa. But since May 2022, numerous monkeypox outbreaks have been identified simultaneously across regions of the world that don’t normally report cases of the disease, sparking fears of a new pandemic.
According to the U.S. Centers for Disease Control and Prevention (CDC), more than 63,100 confirmed monkeypox cases had been recorded around the world in 2022 at the time of writing—the vast majority of those (over 62,500) in locations that haven’t historically reported the disease. While the fatality rate of the current outbreak appears to be low, 10 deaths have been recorded so far in these locations, on top of another 10 in endemic regions.
The authors of a study, published in the open-access journal PLOS Pathogens, documenting the characteristics and spread of the latest outbreak spoke to Newsweek about how the disease appears to behaving in unusual ways.
“Unlike the classical description of monkeypox cases from previous outbreaks, some of the currently reported cases have a different and sometimes atypical clinical presentation and mode of transmission,” Souha Kanj and colleagues at the American University of Beirut Medical Center in Lebanon told Newsweek.
Notably, the sporadic cases or outbreaks that had occurred in non-endemic countries prior to this year were usually linked to people traveling from areas in central and west Africa where the virus is found. But most of the cases reported in this current outbreak weren’t related to travel from endemic countries, according to the authors.
Historically, monkeypox has been documented as producing a similar kind of disease to smallpox, except for the presence of enlarged lymph nodes, which is a symptom not seen in the latter.
Monkeypox usually starts with a first phase of symptoms—such as lethargy, fever and fatigue—followed by lesions described as macular rashes that appear first on the face, before spreading to the extremities. These lesions tend to progress through four distinct stages—known as macular, papular, vesicular and pustular—until they from scabs and fall off.
But in this outbreak: “Monkeypox is behaving differently,” the authors told Newsweek.
“Many patients are presenting with a rash without the first phase,” they said. “Some lesions are confined to one single body region, like the pelvic area.”
For example, one study previously published in the BMJ identified penile swelling and rectal pain as symptoms of the disease among a cohort of people in London, England. These symptoms are not usually associated with the disease.
Another feature of the current outbreak is that several patients who have presented with monkeypox genital lesions also had simultaneous sexually transmitted diseases.
Traditionally, monkeypox was reported to occur after animal-to-human transmission. But in the current outbreak, human-to-human spread is the primary mode of transmission, according to Kanj and colleagues.
“Transmission occurs through large respiratory droplets after a prolonged face-to face contact, or through close contact with infectious skin lesions or bodily fluids, contaminated fomites, surfaces, and objects,” the PLOS authors said. “Skin-to-skin contact seems to be the primary mode of transmission.”
The idea that the disease has been spreading via airborne transmission has also been raised but the authors said this remains “debatable” and is the subject of current investigations.
Also in the current outbreak men have been disproportionately affected compared to women. The virus has primarily infected men who have sex with men (MSM).
Investigating Sexual Transmission
“It remains unclear why MSM are at higher risk, since any person, regardless of gender or sexual orientation might engage in high risk sexual behaviors,” the authors said. “One possibility could be that unprotected anal intercourse is correlated with higher rates of STIs in general and therefore could lead to faster transmission among MSM.”
Meanwhile, the question of whether the monkeypox virus is being transmitted sexually is under investigation.
“Monkeypox was isolated from seminal fluid samples in patients from Italy, however the clinical significance of this finding remains to be established,” the authors said.
Several theories that are awaiting confirmation have arisen to explain why such an unprecedented outbreak has happened now. Firstly, there may have been previous under-detected community spread given that monkeypox occurred in multiple countries during the same period of time, according to the authors.
Secondly, the spread of monkeypox in young populations could be related to the fact that they haven’t received a smallpox vaccination, which provides protection against the disease, given that the viruses are related. The smallpox vaccine was dropped after the disease was declared to have been eradicated in 1980.
“Finally, scientists are still trying to determine whether there are genetic mutations that are responsible for the rapid spread of the monkeypox virus,” the authors said.
Virus Is Mutating
Some evidence has already suggested that the virus is mutating more frequently than expected.
“Multiple sources of introduction and transmission are possible and more thorough investigations are needed to answer these questions,” the authors said.
Kanj and colleagues said the potential for monkeypox to become another pandemic is “less likely” unless the virus evolves differently and acquires the ability to spread through different modes of transmission.
“Transmission requires prolonged contact with the infected person,” they said. “The theory of airborne spread is debatable and under investigation.”
The World Health Organization has declared monkeypox a public health emergency that warrants special attention in light of the unprecedented spread of the virus.
“Physicians from all specialties should be vigilant, as patients with monkeypox might present to any clinic,” Kanj and colleagues said. “More studies are needed to define the clinical evolution of the disease as most data is derived from case series and case reports.”