New variant of mpox might be more contagious

On Monday, the Philippines Department of Health reported a new case of the mpox virus, confirming that a 33-year-old citizen from Metro Manila, with no foreign travel history, tested positive for the viral illness. The patient had developed a fever and a “distinct” rash before the diagnosis. “The mpox virus is among us. This is a warning to everybody,” the Philippines Health Secretary Teddy Herbosa stated during a press conference.

Following the World Health Organization’s (WHO) declaration of mpox as a global public health emergency, several countries have ramped up surveillance and monitoring. The announcement came in light of the ‘new variant’ (clade I) having spread from the Democratic Republic of Congo to neighbouring countries, including Burundi, Kenya, Rwanda and Uganda.

As of now, two mpox are characterised by two clades: clade I and clade II. A clade is a broad grouping of viruses that evolved over time and formed a distinct group. According to the WHO, both variants are transmitted from infected animals to humans, as well as through human-to-human contact. According to the CDC, clade II is endemic to West Africa, while clade I is endemic to Central Africa.

Clade IIb was responsible for the 2022 outbreak, but clade I is believed to cause more severe diseases.

Public health officials have expressed concern about how quickly the new clade I variant seemed to be spreading. However, other experts urge caution about the lethality of the virus. “I think we have to be very, very cautious about saying that this is more dangerous,” said epidemiologist Anne Rimoin from UCLA.

While there are varying reports on the severity of the illness, experts suggest treading with care and awareness, depending on the patients’ overall health. “The data on severity and mortality are still scant. There are many questions about the population it’s spreading in, their immune system, and the transmission route,” said Helen Rees, co-chair Of South Africa’s mpox incident management team.

Since January 2023, more than 22,000 suspected mpox cases, including over 1,200 deaths, have been reported in the DRC. NBC notes: “In the past, outbreaks of clade I have been deadlier than clade II, killing up to 10% of people who got sick. But more recent outbreaks have had lower death rates. Out of an estimated 22,000 cases in this outbreak in Congo, more than 1,200 people have died — which puts the fatality rate at just above 5%.”

“The underlying health conditions of the population in the DRC are probably contributing to the current case fatality rate,” added associate professor Marc Siegel from the Washington School of Medicine and Health Sciences. “With less malnutrition and better access to health care resources, I would imagine that the case fatality rate will not be as high as we’re seeing in the DRC.”

Last week, Sweden reported its first case of mpox clade I, marking the first time that this new variant had been detected outside of Africa. Pakistan also recorded its first case after a 34-year-old man who had recently returned from the Middle East began showing symptoms, though his case involved the clade IIb variant.

The clade IIb strain was behind the 2022 mpox outbreak, leading to around 100,000 cases around the world. Back then, the WHO declared a Public Health Emergency of International Concern (PHEIC), as the virus was being reported in many countries it was not endemic to, while CDC issued travel warnings. But global mortality rates remained low, with a 0.2 percent death rate.

Mpox was first identified in 1958 in lab monkeys in Denmark. In 1970, the first human case was detected in a ten-month-old baby in the DRC. For decades, the disease remained largely confined to tropical African countries until 2003, when cases were reported across the United States, linked to infected pet rodents housed near imported animals from Ghana. The Maryland Department of Health later reported another case in 2021 in a man who had recently travelled to Nigeria.

The WHO warns that people with mpox can become “seriously ill” and the virus can lead to secondary bacterial infections, pneumonia, corneal infections with potential vision loss, and other complications such as encephalitis, myocarditis, proctitis, and in severe cases, death.