Monkeypox –Fleury Notes

Prof. H. Fleury Notes June 2022

This virus belongs to the group of Orthopox viruses including the smallpox virus. It has been known since 1958 to have been identified in an African monkey hence the name monkeypox. In fact its main reservoirs are rodents (rats, mice) and squirrels.

The virus is rampant in Central and West Africa: DRC, Gabon, Ivory Coast, Liberia, Nigeria, Benin, Cameroon, Sierra Leone, Sudan. There are two main strains with different mortality for humans (Central Africa 10% and West Africa 1% mortality).

Humans become contaminated by contact with rodents (bites, aerosols) and by handling monkey meat; in Africa, risk factors include forest or rural habitat, monkey meat handling and care for patients, and non-vaccination (vacciniatric vaccination protects against monkeypox; it was stopped in 1980 by the WHO after the last case of smallpox observed in Somalia in 1977; young populations are therefore no longer protected by cross-vaccination against monkeypox this which explains the current emergence of human cases, particularly in Nigeria). Human-to-human secondary transmission is much lower than that of smallpox. Infected patients returning to Europe or the USA as well as other parts of the world were until now patients who had been contaminated from the animal reservoir. An extra-African episode took place in the USA in 2003 where 70 humans were infected from prairie dogs that had been in contact with rodents imported from West Africa.

The current global epidemic

In recent weeks and the notification of a case of human monkeypox in a patient in London after a stay in Nigeria, an epidemic of monkeypox has been raging around the world especially in men who have sex with men (MSM); in this configuration the transmission would be through body fluids, skin lesions or even respiratory aerosols.

As of 8 June 2022, WHO has reported 1200 cases, including 321 in the UK, 198 in Portugal, 191 in Spain, 113 in Germany, 100 in Canada, 66 in France, 54 in the Netherlands and 39 in the USA (list not complete).

Pathophysiology and clinic

After the entry of the virus and whatever the route, there is local multiplication at the lymph node level and then viremia (passage of the virus into the blood) with a diffusion to other organs. Incubation is 5 to 14 days or even 21 days. The onset of clinical signs corresponds to a second viremia: fever, lymphadenopathy, headache, myalgia, fatigue then appearance of mucous lesions in the mouth and a centrifugal rash starting in the face and spreading to the extremities (palms, soles of the feet); the papules become vesicles and then pustules of 2 to 10mm before turning into crusts that flaking in 7 to 14 days. Healing is achieved in 3-4 weeks.  Warning: the patient is considered infectious until the crusts fall.

Complications are rare with monkeypox (especially with the West African strain that currently concerns us): pneumonia, sepsis, encephalitis.

Diagnosis and treatment

Differential diagnosis is made with chickenpox and of course with smallpox. An Orthopox virus PCR is used followed by a monkeypox-specific PCR if the first PCR is positive.

The patient is isolated and wears a mask. Contact cases are vaccinated with a 3rd generation smallpox vaccine (Ankara strain) before the 4th day after exposure (2 injections 4 weeks apart)

In case of aggravation, the patient can benefit from antiviral drugs: tecovirimat which inhibits viral exit from the infected cell; cidofovir which causes inhibition of viral DNA synthesis after incorporation into the chain being synthesized and cessation of elongation.

Commentary on the Science article of June 8, 2022

Superb article that asks an original and fundamental question.

Will infected patients in various parts of the world outside Africa contaminate animals locally, becoming reservoirs for a transition to endemic?

I recall that in Ohio in the USA, deer have been infected with SARS CoV2 and now represent a potential reservoir for humans. On the other hand, it cannot be excluded that virus replication in animals generates mutants that are more pathogenic to humans.