Monkeypox: is virus related to smallpox or chickenpox, does smallpox vaccine prevent it, and symptoms compared

Up to 29 August 2022, there were 3,279 confirmed and 134 highly probable monkeypox cases in the UK. Of these, 85 were in Scotland, 27 were in Northern Ireland, 44 were in Wales and 3,257 were in England, the UK Health Security Agency (UKHSA) has said.

Monkeypox has also been listed as a notifiable disease in law since 8 June, which means all doctors in England are required to notify their local council or local Health Protection Team (HPT) if they suspect a patient has monkeypox.

Laboratories must also notify the UKHSA if the monkeypox virus is identified in a laboratory sample.

But what is monkeypox and is it related to chickenpox and smallpox?

Here’s what you need to know.

What is monkeypox?

Monkeypox is a rare disease caused by infection with the monkeypox virus.

Most cases have been in Africa and the risk of catching monkeypox in the UK is very low, the NHS explains.

There have only been a very small number of cases of monkeypox in the UK and when there is a case, health professionals will aim to contact anyone who has been in close contact with the infected person.

The NHS website says: “If you have not been contacted, be reassured you are extremely unlikely to catch monkeypox.”

What are the symptoms of monkeypox?

The illness begins with:

• high temperature
• headache
• muscle aches
• backache
• swollen glands
• chills
• Exhaustion

A rash then usually begins one to five days after the first symptoms appear. The spots often start on the face before spreading to other parts of the body.

During the illness, the rash then changes from raised red bumps, to spots filled with fluid, with the spots eventually forming scabs which later fall off.

Is it related to smallpox or chickenpox?

According to the World Health Organisation (WHO), the clinical presentation of monkeypox resembles that of smallpox, as it is a related orthopoxvirus infection, but smallpox was eradicated worldwide in 1980.

Monkeypox symptoms are similar to those seen in the past in smallpox patients, but it is clinically less severe.

Lymphadenopathy, which is the swelling of the lymph nodes, is also a distinctive feature of monkeypox compared to other diseases that may initially appear similar, such as chickenpox.

Monkeypox and smallpox are both caused by members of the poxvirus family, but chickenpox is caused by the Varicella zoster virus and is not related to the poxviruses.

WHO said: “Lymphadenopathy during the prodromal stage of illness can be a clinical feature to distinguish monkeypox from chickenpox or smallpox.”

Hussain Abdeh, superintendent pharmacist at Medicine Direct, also noted that the rash associated with monkeypox is often mistaken for chickenpox, and “it is only when the spots become lesions and blisters that the error is corrected”.

Does smallpox vaccine prevent monkeypox?

Martin Michaelis, professor of molecular medicine at the University of Kent, said the smallpox vaccine is anticipated to also protect from monkeypox.

However, it is possible we see more monkeypox cases because fewer people are protected against smallpox due to a lot of smallpox vaccinations programmes being stopped after the disease eradication.

The USA currently has licensed a vaccine against smallpox and monkeypox.

Health Secretary Sajid Javid recently confirmed that the UK has “procured further doses of vaccines that are effective against monkeypox”.