Ad-hoc update: Monkeypox

26 May 2022

Following several requests after this week’s Covid-19 missive, I am sending this short missive about monkeypox, mainly intended for those not familiar with this virus.

Monkeypox was first identified in a lab monkey in 1958 – hence its name. However, its name is a misnomer as the natural host is not monkeys – it is small rodents. The first human case was reported in 1970 – in Africa and it has led to sporadic outbreaks since then, mostly in Africa. Monkeypox is a DNA virus and not an RNA virus (like SARS-CoV-2) or a retrovirus (like HIV). 

It is not an easily transmitted virus. It spreads through close contact with infected animals (note that some domestic animals can also get infected and pass the virus to humans, though this is rare). Human-to-human transmission in uncommon and requires prolonged close contact, just like smallpox transmission.  It is therefore surprising to see such widespread global distribution – leading to conjecture that the monkeypox strain in circulation now may be more transmissible that the past strains. 

A key issue is that there is no evidence of pre-symptomatic transmission of monkeypox – transmission coincides with onset of symptoms – hence testing and identification of cases is an essential step in containment, which has usually been achieved in past outbreaks through case-finding and isolation of cases.

For prevention, a highly effective monkeypox was licensed with the FDA in 2019, before the Covid-19 pandemic – though stocks of this vaccine are not readily available. The available stocks of the monkeypox vaccine and stockpiled smallpox vaccines are being used for “ring vaccination” to protect those possibly exposed by an identified contact. For those of you who were born before 1970, you were likely to have been vaccinated against smallpox and are protected, at least partially, as the smallpox vaccine is effective against monkeypox. It should be noted that all the standard precautions like social distancing and masks that we use for Covid-19, are also effective against the spread of monkeypox. 

With regard to symptoms, it presents with fever, cough, etc and a rash that looks like chickenpox. The condition is usually mild in adults but there is an increased risk of severe disease in children and immunocompromised individuals, where case fatality rates can be as high as 1%.

While monkeypox could conceivably become a pandemic (almost anything is possible after Covid-19), this is a highly unlikely scenario as this infection has been readily contained in past through case-finding and isolation only.

I hope this helps those of you who asked for information on monkeypox. 

Salim S. Abdool Karim, FRS
Director: CAPRISA
CAPRISA Professor of Global Health: Columbia University