Why the Africa mpox outbreak is so worrying

Alarmed by the sharp rise in mpox cases, the Africa Centres for Disease Control has made the unprecedented decision to designate the outbreak affecting African countries a continental public health emergency.

The World Health Organization (WHO) is likewise convening to determine whether the epidemic warrants its highest global alert level.

The decisions follow the rapid spread of a highly virulent form of the disease across 16 countries, with six additional countries reporting cases within 10 days.

Since the start of 2024, Africa has recorded 15,132 confirmed mpox cases. Countries reporting infections include Burundi, Cameroon, Congo, Ghana, Liberia, Nigeria, Rwanda, the Democratic Republic of Congo, South Africa, Uganda and Kenya.

Virologist Cheryl Walter explains why the current mpox outbreaks are causing such serious concern.

How many mpox strains are there, and which are most concerning?

Mpox belongs to the pox virus family, alongside viruses such as smallpox and cowpox. It is marked by a rash, followed by raised bumps on the skin. In mpox, these bumps fill with fluid before eventually forming scabs.

As diseases including COVID-19 have shown us, viruses undergo genetic changes and can mutate rapidly.

Mpox is no exception, although pox viruses generally change far more slowly than viruses such as HIV. HIV mutates roughly every three times an individual virus replicates.

There are two mpox strains: clade I and clade II. They can be thought of as two large branches of the same tree.

Until around five or six years ago, these clades showed relatively little diversity.

That has now changed. The branches are expanding and developing more leaves. New subclades have emerged within both clade I and clade II, effectively creating two further offshoot branches.

Clade II is considerably less dangerous, with a case fatality rate of around 0.1%. Put another way, about one person in every thousand dies.

Scientists are now reporting thousands of clade I cases across 16 African countries, alongside a case fatality rate of between 3% and 4%. This equates to three or four deaths for every hundred people infected. Children account for many of the cases.

COVID-19 provides a useful comparison. It was classified as an international public emergency between 30 January 2020 and 31 December 2021, and its estimated case fatality rate was 1.2%.

Mpox remains a comparatively under-researched virus. Until recently, only a small number of confirmed cases were identified each year. It was mainly found in tropical rainforest regions of central and west Africa, giving the virus few opportunities to adapt to humans.

It is not yet clear whether genetic changes are allowing these viruses to spread more readily, or whether the variants currently circulating are more dangerous.

What is known is that the virus is changing while passing through large numbers of people. A virus can mutate only as it moves through a host, such as a human.

The more hosts it infects, the more chances it has to change and potentially become more virulent or more transmissible.

Because this virus is now moving through many people, it has many more opportunities to do so.

How does mpox spread into new areas?

The virus can be transmitted through contact, including sharing utensils, plates, towels and bedding.

Women and children are affected disproportionately because frequent skin-to-skin contact brings them into close contact daily. Children play together at schools and nurseries, regularly touching objects as well as one another.

Viruses also transmit easily in densely populated, low-income communities, where people may be unable to isolate because they need to earn an income.

Two further factors helping mpox spread rapidly are its lengthy incubation period and its non-specific symptoms.

The incubation period varies substantially, lasting from five to as long as 21 days. During that time, someone may contract mpox, travel to another country and pass the disease on to other people.

Early symptoms are non-specific, including swollen glands, fever and generally feeling unwell. An estimated 10% of people infected with mpox have no symptoms.

It may be only once the rash develops that it becomes clear the illness is not a cold, flu or COVID-19.

This is made more difficult in children, whose rashes may be confused with chickenpox or another common childhood infectious disease.

What emergency measures are needed to stop the mpox outbreak becoming a pandemic?

African health agencies seeking to control the virus face several obstacles.

Resources for fighting the disease are scarce, and vaccine shortages are a major concern. The Africa Centres for Disease Control estimates that African countries have only 200,000 doses available, despite needing at least 10 million.

Even so, much can still be done.

Testing: This is the most important tool in the response. Authorities need to identify where cases are occurring and who mpox is passing through within communities. The information must also be used for contact tracing. Simple lateral flow tests can be used, with a nasal and/or throat swab taken in the community and results available within 30 minutes.

Messaging: During the previous worldwide outbreak, much of the communication was directed at sex workers and men who have sex with men. This may have led people to believe that mpox is solely a sexually transmitted disease. It is not.

As women and children are now contracting the virus, communities must be informed about the symptoms to watch for and the actions they should take.

Vaccinating: Since mpox is very similar to smallpox, the smallpox vaccine can be used. However, stockpiles are limited and smallpox vaccines cannot be manufactured quickly enough. The WHO has requested vaccine candidates for rapid approval and distribution.

These and other measures must be introduced urgently to contain and suppress this epidemic before it could potentially develop into a global pandemic.

Cheryl Walter, Senior Lecturer in Biomedical Science, University of Hull

This article is republished from The Conversation under a Creative Commons licence. Read the original article.