Recently, the United Kingdom, the United States, Portugal, Spain, Italy, Sweden, Australia and other countries reported confirmed or suspected cases of human monkeypox virus infection. So, what is monkeypox virus? How does it spread? Is it necessary to worry about a large-scale outbreak of this infectious disease?
Viral zoonosis
Monkeypox is a viral zoonosis. Its pathogen monkeypox virus is a DNA (deoxyribonucleic acid) virus, belonging to the genus orthopoxvirus of poxviridae. It is "close relative" to smallpox virus that has been raging for thousands of years in human history. Monkeypox virus was first discovered in 1958. At that time, a group of monkeys used for research had a "pox like" infectious disease, so it was named. Since the World Health Organization announced the complete elimination of smallpox in 1980, monkeypox virus has become the normal pox virus with the greatest impact on public health.
Monkey pox was confirmed by the WHO website for the first time, but its host may be the monkey pox. In Africa, it has been found that animals such as squirrels, Gambian rats and different kinds of monkeys may be infected with monkeypox virus.
It is reported that monkeypox virus is mainly prevalent in West and Central Africa. In 1970, the first human case of monkeypox infection was found in the Democratic Republic of the Congo. Since then, most of the cases reported globally have been distributed in African countries such as Congo (DRC), Congo (Brazzaville), Central African Republic, Nigeria and Cameroon. For example, Congo (DRC) reported more than 6000 cases of monkeypox infection in 2020 and more than 3000 cases in 2021.
The cumulative number of human infections of monkeypox in Gambia and Africa can be traced back to the United States in 2003. Since 2018, people infected with monkeypox virus have been found among passengers from Nigeria in Israel, the United Kingdom, Singapore and other countries.
Direct contact with the blood, body fluid, skin or mucous membrane damaged parts of infected animals may cause monkeypox virus to spread from animals to humans. Eating improperly cooked infected animals is also a risk factor for "animal to human". In general, monkeypox virus transmission between people is not common. Interpersonal transmission routes include close contact with respiratory secretions, skin damaged parts or contaminated items of infected persons. It usually takes a longer time to spread respiratory droplets face to face. In addition, monkeypox virus may be transmitted from mother to child through placenta or close contact during childbirth.
Who stressed that in order to reduce the risk of infection, in areas where monkeypox virus is prevalent, contact with wild animals should be avoided, especially unprotected contact with the meat, blood or other parts of sick or dead animals. Edible meat must be thoroughly cooked.
Smallpox vaccine is effective against monkeypox
According to the who, the symptoms of monkeypox virus infection are similar to smallpox, but the clinical severity is mild. The incubation period is usually 6 to 13 days and may be as long as 21 days. Early symptoms include fever, headache, enlarged lymph nodes, muscle soreness and severe fatigue. Enlarged lymph nodes help to distinguish monkeypox from smallpox. After a few days of fever, it develops into a large-area rash on the face and other parts of the body, which may lead to secondary infection, bronchopneumonia, sepsis, etc.
Monkeypox is usually a self limiting disease, and most patients recover within a few weeks. Severe cases are common in children or people with immune deficiency, and are also related to the basic health status of infected people, the degree of exposure to virus and the severity of complications. The mortality of monkeypox varies greatly, ranging from 3% to 6% in recent years.
Studies have shown that the effective rate of vaccination against monkeypox is 85%. In 2019, a vaccine based on attenuated vaccinia virus was approved to prevent monkeypox, but it has not been widely vaccinated. In terms of treatment, tecovir, an anti smallpox drug previously approved by the U.S. Food and drug administration, was approved in Europe in 2022 for the treatment of monkeypox and has not been widely used.
The recent spread is characterized by "atypical"
In recent days, the number of countries and infected cases reporting monkeypox cases outside Africa has been increasing, and many infected people have no travel history in monkeypox endemic areas. The World Health Organization said that monkeypox cases without direct travel links with epidemic areas have occurred in many "non epidemic countries", which is an "atypical" situation, and the source of infection is still being investigated.
Does this mean that monkeypox virus has become more infectious? Michael Ryan, executive director of the WHO health emergency project, said at a press conference recently that the epidemiology of monkeypox has changed and its scope has expanded in the past few years. In West Africa and the Sahel, with the increase of climate pressure, humans and animals have to adapt to the environment in order to survive, which may make animal populations closer to humans and sometimes compete for the same food resources. We must really understand the deep ecology and human behavior in relevant areas, so as to try to prevent the spread of this disease to humans from the source of nature.
Anne rimoyin, Professor of epidemiology at UCLA, pointed out that the increase in monkeypox cases may be related to the elimination of smallpox. After 1980, people were no longer vaccinated against smallpox, and their immunity to monkeypox also decreased. According to the research released by rimoyne and her colleagues in 2010, the monkeypox incidence rate in the DRC has increased by more than 14 times in the past 30 years, from less than 1 case per 10000 people to about 14 cases per 10000 people.
Another puzzling phenomenon is that many people infected recently are gay, bisexual or other men who have sex with men. Michaelhead, senior researcher on global health issues at the University of Southampton, UK, said that monkeypox virus could not be confirmed as a sexually transmitted virus similar to AIDS virus. "Close contact during sexual behavior or intimate activities, including long-term skin contact, may be a key factor in transmission".