The monkeypox virus

The monkeypox virus is an enveloped double – stranded DNA virus with a rectangular shape, belonging to the Orthopoxvirus genus of the Poxviridae family. The following is some specific information about the monkeypox virus:

1. Relationship with other viruses:
   • The monkeypox virus belongs to the Orthopoxvirus genus, along with the smallpox virus, cowpox virus, and vaccinia virus (used to prepare smallpox vaccines). These viruses are very similar in terms of antigenicity, biological characteristics, morphology, structure, and resistance. Therefore, those who have been previously vaccinated against smallpox have some cross – protection against the monkeypox virus.
2. Classification: There are two different genetic evolutionary branches of the monkeypox virus, namely the Central African clade and the West African clade. The West African clade is less pathogenic to humans, with a case – fatality rate of about 3.6%; while the Central African clade is more pathogenic to humans, with a case – fatality rate as high as 10% in the absence of smallpox vaccination.
3. Transmission:
   • Animal – to – human transmission: The main hosts of the monkeypox virus are African rodents (such as African squirrels, tree squirrels, Gambian pouched rats, dormice, etc.). Primates (various monkeys and apes) can occasionally become infected through contact with infected rodents. Humans can be infected by being bitten by infected animals or through direct contact with the blood, body fluids, or monkeypox lesions of infected animals.
   • Human – to – human transmission: It is generally believed that it spreads through a large number of virus – containing respiratory droplets during direct, long – term face – to – face contact. In addition, it can also spread through direct contact with the body fluids of infected persons or items contaminated with the virus, such as clothes and bedding. The virus can also spread from pregnant women to fetuses through the placenta.
4. Symptoms after infection:
   • Incubation period: It is about 5 to 21 days, mostly 6 to 13 days.
   • Early stage of illness: There may be chills and fever (body temperature is mostly above 38.5 °C), accompanied by symptoms such as headache, lethargy, fatigue, back pain, and myalgia. Most patients may have swollen lymph nodes in areas such as the neck, armpits, and groin. Compared with diseases such as chickenpox, measles, and smallpox, swollen lymph nodes are a distinct feature of monkeypox.
   • Rash stage: The rash first appears on the face and gradually spreads to the limbs and other parts. It can also affect the oral mucosa, digestive tract, genitals, conjunctiva, and cornea, etc. The number of rashes ranges from several to several thousand; the rash changes from maculopapules to small vesicles, pustules, and finally scabs. It takes about 2 to 4 weeks from the onset of the disease until the scabs fall off. After the scabs fall off, erythema or pigmentation may remain, and even scars may form, and the scars can last for several years.
5. Nature of the disease: Monkeypox is a self – limiting disease. Most cases have mild symptoms, but newborns, children, and people with underlying immunodeficiency diseases may face more severe symptoms and the risk of death from monkeypox.

The monkeypox virus was first detected in monkeys, but both humans and animals can be infected and can transmit the virus to each other. Since September 20, 2023, China has classified monkeypox as a Class B infectious disease and adopted prevention and control measures for Class B infectious diseases.