Mpox or monkeypox is back in the spotlight, two years after the last outbreak in which hundreds of cases were also registered in the Netherlands. Virologists and the WHO are concerned about the spread of the virus in Eastern Congo. At the end of last year, a new variant emerged in the province of South Kivu. The virus is believed to have gained a foothold among sex workers and their clients in the mining town of Kamituga.
Since then, the number of cases has been steadily increasing, and the new mpox variant has now been reported in neighboring Rwanda and the Central African Republic. There is a one to two week delay between infection and the development of symptoms, which contributes to the spread. As of August 9, the counter in the whole of Africa stands at 2,822 confirmed cases, 14,719 suspected infections and as many as 517 deaths. Children are particularly vulnerable: of the almost 8,000 infections and 384 deaths in Congo in the first half of 2024, more than half were under the age of 15.
Children and families
Although sex workers and their clients are a hub in the rapid spread, and therefore a risk group, mpox is not considered a sexually transmitted disease. Transmission can also occur within households and schools through skin contact, via respiratory droplets from an infected person or touching contaminated surfaces, bedding and kitchen utensils, and pregnant women can also transmit the virus to their child. This explains the current wave of infections among children and families.
In the fall of 2022, mpox was also prominent in the news. Between May 2022 and May 2023, at least 90,000 people in 111 countries were infected worldwide, resulting in 141 deaths. The fact that the number of fatalities is already much higher with a much lower number of infections illustrates that this variant is more deadly. The fact that this outbreak claims more victims is because this mpox variant belongs to a more virulent group. The 2022 outbreak was caused by a relatively mild clade II virus from Nigeria, behind the current outbreak is a more aggressive clade I virus. Clade I viruses cause more severe symptoms and a higher risk of extensive, contagious rash. The mortality rate – case fatality rate – by a clade I infection is estimated at 10.6 percent, versus 3.6 percent for a clade II infection.
Virulent
Why clade I mpox is more virulent than clade II is a subject of research and discussion. The 200,000 base pair mpox genome codes for over 170 proteins, which are 99.4 percent identical between the two virus groups. However, there are some striking differences. In clade II, some viral genes are shortened or even absent, which clade I viruses do have. It is possible that (some of) these genes play a role in manipulating or evading the immune response. However, there is no experimental evidence for this, partly due to the lack of suitable animal models.
The DNA of the clade I mpox variant from eastern Congo has now been mapped. Compared to mpox from wild rodents, a handful of mutations can be seen in the virus DNA. Five of these mutations are a signal of repeated virus replication in humans. In Africa, mpox is endemic, especially among rodents and primates. Sometimes the virus jumps to humans through hunting, trade and consumption of wild animals. Spread between humans did not play a significant role for decades, until 2022. The researchers estimate that the new variant must have jumped from animal to human sometime around September 2023 and has since found its way through human contact. The fact that mpox is increasingly being reported has something to do with human smallpox vaccination, which also protected against monkeypox. Since the cessation of smallpox vaccination in 1974, the population group that has no immunity has gradually grown: older people still have some immunity to mpox, younger people do not.
Accelerated admission
Infections between people plus a more deadly course of the disease are reasons for the WHO to raise the alarm. Vaccine manufacturers working on an mpox vaccine that is not yet on the market were recently called upon to submit a dossier to the WHO for accelerated approval. During the 2022 outbreak, vaccination has already taken place on a small scale in Africa, but vaccination rates are low, especially in eastern Congo.
On Wednesday, August 14, the WHO’s long-awaited decision to declare the outbreak Public Health Emergency of International Concern (PHEIC). This also happened in July 2022, which led to more money for research and coordination, education and vaccination of risk groups. These measures brought the outbreak to a halt relatively quickly. The declaration of a health emergency by the WHO will focus money and attention, but it may take weeks to months before people in Central Africa feel the effects. At the same time, the European Centre for Disease Prevention and Control (ECDC) sees no risks for European countries, due to better medical facilities and immunity after infection and mpox vaccination in 2022.
