Overview of Monkeypox

Monkeypox is caused by the monkeypox virus. Monkeypox virus is a virus belonging to the genus Orthopoxvirus of the Poxviridae family. Monkeypox virus has the typical shape of Orthopox virus, with a rounded brick shape or an oval shape and a size of 200-400 nm. The virus is enveloped by a lipoprotein membrane with two protein-containing side bodies in the middle. The virus has a thick membrane core containing a large double-stranded DNA genome.

The monkeypox virus genome is double-stranded DNA, about 197 kb in length, containing an inverted terminal repeat sequence in the same but opposite direction at the end of the genome. The virus contains 190 open reading frames, 4 of which are located in inverted terminal repeats. Among them, the content of guanine (G) and cytosine (C) is very low, accounting for about 33%. The study found that the virus has hemagglutinin, which can agglutinate chicken red blood cells. In terms of physicochemical properties, monkeypox virus is between smallpox virus and vaccinia virus. Clinical studies have shown that monkeypox virus is resistant to ether and desiccation, but is easily inactivated by chloroform, methanol and formalin. In addition, heating at 56 °C for 30 minutes is also easy to inactivate it. It can maintain long-term viability at 4 ℃ and -70 ℃, and the storage period at -20 ℃ is shorter.

The Host of Monkeypox Virus

Monkeypox virus can grow and produce significant cytopathic effects in primary, secondary and passaged cells derived from monkeys, rabbits, cows, guinea pigs and mice, as well as humans. Cavities or plaques were formed on monolayer cells, and also on chicken embryo fibroblasts. Most of the infected cells contained many small round or oval eosinophilic inclusion bodies. Chicken embryos are more sensitive to pox virus, and different virus strains can produce different types of inclusion bodies, so they can be identified by the difference in the shape and size of pox blisters. The upper temperature of monkeypox virus culture is 35 ℃, and it forms opaque, white, flat pox blisters on the chorion of chicken embryos. All monkeypox virus strains can grow well on chick chorioallantoic membrane, and can cause chorioallantoic membrane edema and small white pox spots. The antigens of each strain of monkeypox virus are the same, and have common structural and soluble antigens with other orthopoxviruses. Difficulty distinguishing from variola virus and vaccinia virus in complement fixation assay and agar diffusion assay.

The Host of Monkeypox Virus

Monkeypox virus can grow and produce significant cytopathic effects in primary, secondary and passaged cells derived from monkeys, rabbits, cows, guinea pigs and mice, as well as humans. Cavities or plaques were formed on monolayer cells, and also on chicken embryo fibroblasts. Most of the infected cells contained many small round or oval eosinophilic inclusion bodies. Chicken embryos are more sensitive to pox virus, and different virus strains can produce different types of inclusion bodies, so they can be identified by the difference in the shape and size of pox blisters. The upper temperature of monkeypox virus culture is 35 ℃, and it forms opaque, white, flat pox blisters on the chorion of chicken embryos. All monkeypox virus strains can grow well on chick chorioallantoic membrane, and can cause chorioallantoic membrane edema and small white pox spots. The antigens of each strain of monkeypox virus are the same, and have common structural and soluble antigens with other orthopoxviruses. Difficulty distinguishing from variola virus and vaccinia virus in complement fixation assay and agar diffusion assay.

Monkeypox Virus Infection

Monkeypox patients, host animals, and infected animals are the main sources of infection of the disease. Monkeypox virus is ubiquitous in nature, and the main natural hosts are monkeys and squirrels inhabiting tropical rain forests and infected rodents or other mammals.

Propagation Mode

The disease is mainly transmitted by animals, and humans can contract monkeypox through bites from infected animals or direct contact with the blood, body fluids and rashes of infected animals. In addition, the virus can also be transmitted from person to person. According to records, in the investigation and statistical analysis of monkeypox cases that occurred in Congo from 1986 to 1988, it was found that most of the cases (about 72%) were mainly transmitted directly to humans through animals, and the susceptible population was children not vaccinated against smallpox. However, in the monkeypox outbreak cases in 1996-1997, it was found that monkeypox changed the transmission route to humans. The survey showed that most cases (about 78%) were transmitted from person to person, which made this outbreak. Lasted over a year.

Susceptible Population

All age groups can contract the disease, but unvaccinated children have a high risk of death, with a fatality rate of about 10%.

Clinical Symptoms

Clinical symptoms are similar to those of smallpox, but are usually milder. The incubation period of the disease is generally 12 days, and the average disease duration is 2-4 weeks. The prodromal phase usually lasts 2-5 days, with fever, headache, myalgia, back pain, swollen lymph nodes, general malaise and fatigue, and occasionally abdominal pain or throat pain. During the rash stage, the patient develops a smallpox-like rash all over the body. The rashes with a diameter of 1-4 mm are numerous and scattered, and usually occur on the eyelids, face, trunk, limbs, palms, feet and genitals. The number of rashes is variable, but it can simultaneously occur, that is, through maculopapular rash, blisters, pustules, crusting and then scarring. During the final recovery period, the rash subsides, after which the symptoms gradually improve. The clinical features of monkeypox are very similar to those of common smallpox, except that monkeypox may have more swollen lymph nodes.