Monkeypox can spread asymptomatically, the scientists interviewed by Izvestia did not exclude. Foreign experts have already proved such a possibility in 2017, but they did not investigate the strain of the virus that is now spreading. Then the authors of the work found antibodies to monkeypox in people who had contact with animals – potential carriers of the pathogen. However, the participants in the experiment did not report any symptoms of infection. According to experts, there is a small chance that asymptomatic carriers may be people who have not been vaccinated against smallpox. But the contribution of such distributors to the overall epidemic picture will be negligible, since in the vast majority of cases the characteristic signs of the disease still appear.

Widespread and dangerous

The reason for the unexpected spread of monkeypox among people in European countries and the United States may be the existence of asymptomatic carriers of the virusepidemiologists suggest.

People vaccinated against smallpox retain immunity throughout their lives, but no one has studied how much it prevents the “carrier” of the monkeypox virus., – Alexei Agranovsky, professor of the Department of Virology at the Faculty of Biology of Moscow State University, told Izvestia. — An unvaccinated person can be an asymptomatic carrier, but is unlikely to be. Characteristic symptoms appear in most cases of infection.

Photo: REUTERS/Christinne Muschi

Evidence that monkeypox can spread asymptomatically was obtained by foreign scientists back in 2017.. Specialists from the US Centers for Disease Control and Prevention and the Ministry of Health of Cameroon explored circulation of the virus in humans following an outbreak of monkeypox among chimpanzees in Cameroon.

The infection was recorded in the reserve of primates in 2016 A year later, scientists conducted a survey and took a blood test for antibodies to OPXV (a genus of viruses that also includes the monkeypox virus MPXV) from the staff of the reserve and the inhabitants of four villages nearby. There were 125 people in total. The age of the participants ranged from 18 to 83, and half were born after routine smallpox vaccination ended in 1980. However, researchers did not have reliable information about who was vaccinated and who was not.

Antibodies to OPXV found in a third of the participants in the experiment. However among 63 people born after vaccination was discontinued, only four had a positive result, and with sick chimpanzees during the outbreak in 2016 they did not contact. Interestingly, one participant tested positive for IgM (antibodies that are first produced in humans after exposure to a pathogen) to OPXV, indicating very recent exposure to this type of virus. This person said that he often went out into the forest and met with Gambian rats and squirrels from January to October 2017. Most of the participants also reported contact with these animals, as well as with porcupines.

– Despite the name, monkeys are not involved in the spread of this type of smallpox. They were infected from rodents that can infect other animals as well,” explained Sergey Chudakov, head of the Preventive Medicine direction of the Healthnet National Technological Initiative market.


Photo: TASS/Cecilia Fabiano

None of the subjects reported having any symptoms similar to monkeypox.. It means that many study participants were infected with the monkeypox virus, probably from wild animals, but the disease was very mild or asymptomatic for them, scientists came to the conclusion.

“We identified the presence of antibodies in participants younger than smallpox vaccination age in the Cameroon region, suggesting undetected or possible asymptomatic circulation of an OPXV member in human populations in this region,” the authors concluded.

Not the same anymore

It is likely that the monkeypox virus now spreading is very different from the one that circulated in Cameroon in 2016-2017.. As Izvestia wrote, the causative agent of infection has mutated in the last five years. A change in the genome of the virus indicates that the pathogen is able to multiply in the human body, and inheritance may be associated with sustained transmission from person to person, indicated in article scientists from the Institute of Evolutionary Biology, University of Edinburgh (UK).

It is possible that the monkeypox virus may be asymptomatic, but this needs to be experimentally confirmed, Sergey Netesov, head of the laboratory of biotechnology and virology of the Faculty of Natural Sciences of Novosibirsk State University, emphasized in an interview with Izvestia.


Photo: REUTERS/Lukas Barth

According to Pavel Volchkov, head of the MIPT Laboratory of Genomic Engineering, the likelihood of a person being an asymptomatic carrier of monkeypox is low.

“A person carries a huge amount of viruses that have adapted to the host’s body and coexist without harm to it,” the scientist explained. “But smallpox viruses are quite large, so they carry a large number of genes necessary for their life, they do not quickly and easily adapt to new hosts. Without this condition, asymptomatic carriage is unlikely to succeed.

However, MPXV has been “familiar” with humans for over fifty years, and has repeatedly “tried” to move from animals to humans. Perhaps there is something new in the current version of the virusPavel Volchkov said.

Rospotrebnadzor already published recommendations on the organization of anti-epidemic measures in medical organizations in the detection of monkeypox patients. Among them, strengthening measures to identify people with symptoms who arrived from epidemically disadvantaged countries.

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