Monkeypox: Why the disease spreads around the world after being endemic for decades in Africa

The monkeypox virus, which causes the disease popularly known as monkeypox, has been studied for decades and has been detected in at least eleven African countries since the 1970s. But why has it started to spread to other parts of the world just now?

So far, there are no definite answers to this question. But scientists list at least five hypotheses that would help understand why the disease has become an international public health emergency.

Among the factors raised by experts heard by BBC News Brasil, are the neglect of neglected diseases, the increase in the mobility of people with the end of restrictions related to Covid, the lack of immunity of the population against the viruses of this family, a pattern of transmission and a mixture of all these factors.

‘Signs were clear’

Virologist Clarissa Damaso, from the Federal University of Rio de Janeiro (UFRJ), has spent the last 35 years of her career studying orthopoxviruses, a family of infectious agents that includes monkeypox and the cause of smallpox, among others.

She is also an advisor to the World Health Organization (WHO) and integrates committees on research and public policies related to these infectious agents.

According to the scientist’s assessment, it was only a matter of time before the monkeypox spread took place.

“One hour or another, a situation like this would break out. The issue is that we do not pay attention to the signs that come from less developed countries”, he analyzes.

“And the signs were clear: the number of cases was increasing little by little. First, through human contact with infected animals in wild areas. Then, in regions close to larger cities.”

“To top it off, more and more people are going to work or walk in areas where this virus is endemic,” he adds.

“It is worth remembering that this disease has never disappeared from the radar, and we have already had other smaller outbreaks, of few cases, recorded outside Africa in recent years”, agrees infectologist Mirian Dal Ben, from Hospital Sírio-Libanês, in São Paulo.

This whole process means that people’s contact with monkeypox became more and more common – until cases began to be “exported” to other continents more frequently and generated the chains of transmission observed in the last three months.

wrong time

Damaso adds a second factor that helps to understand the current health crisis: it is unfolding at a time when most restrictions related to the covid-19 pandemic have been completely abandoned by countries.

“The monkeypox outbreak happens at the wrong time, in a period right after the covid crisis, when people felt freer, went to have fun and gathered”, contextualizes the virologist.

From what was released by authorities in late May, the first wave of monkeypox cases appears to be related to parties that took place in Spain and Belgium.

Possibly, one or several people who participated in these events were infected, had contact with many people and passed the virus on.

This, in turn, created chains of transmission of the pathogen in the community, which, in a scenario of increased international travel and post-covid face-to-face meetings, quickly spread across cities, countries and continents.

But that still doesn’t fully answer why this disease has spread right now – and not at other times in the past, when displacements, agglomerations and parties also happened.

“Why did monkeypox take so long to affect other places? This is still a mystery to us”, admits physician Alexandre Naime Barbosa, vice president of the Brazilian Society of Infectious Diseases.

A modified virus?

One of the first hypotheses that would help explain the current outbreak would be some new mutation in monkeypox, which would make it more transmissible between people, for example.

The scenario, however, is considered very unlikely by experts. This pathogen has DNA as its genetic code, which means that it is much more stable and carries internal mechanisms to repair genomic errors – unlike the coronavirus, which is made up of RNA and mutates at a much higher frequency.

Genetic sequencing of samples taken from patients in recent weeks also helps to rule out this theory: the virus in circulation now does not appear to show significant changes in the genome when compared to versions of the pathogen analyzed in previous years.

Damaso explains that the monkeypox subtype that is operating in several countries has a lower lethality and, despite not having suffered major mutations in the genetic code, it may have acquired a kind of “pattern of passage”.

It is worth remembering here that the main form of transmission occurs through direct and prolonged contact with the characteristic wounds of this disease – other possibilities of infection are the droplets of saliva (which can carry the virus) and the sharing of personal objects (such as towels, bedding, plates, glasses and cutlery).

“To date, most cases are happening in men who have sex with other men, and they commonly have lesions in the genital region,” he describes.

“Contact with these wounds is usually more intense during sexual intercourse. From there, the virus is transmitted to another individual, who also tends to manifest symptoms in the genital region”, he adds.

In other words, the pattern of passage happens due to close contact with the lesions, which in the current outbreak appear more frequently in the genital region. Thus, the infected person also develops lesions in that part of the body – and can perpetuate the cycle by having more intimate contact with other individuals.

But this, of course, does not rule out the relevance of other forms of transmission of this infectious agent that go beyond sexual intercourse, such as the sharing of objects and droplets of saliva. Proof of this are the recently confirmed cases in children.

Outdated protection?

The second hypothesis that would justify the spread of monkeypox now has to do with the unpreparedness of our defense cells to deal with this family of viruses.

This is because orthopoxviruses have a peculiar characteristic: if you have already had contact with one of them, you are relatively well protected from being infected by the others. It is a kind of “cross-immunity”.

And that’s where vaccination against smallpox comes in, a disease caused by smallpox (also an orthopoxvirus) that has been completely eradicated from the planet.

The application of doses was suspended worldwide from the end of the 1970s – after all, this virus stopped circulating among us and no longer represented a threat.

Some studies reveal that people who were vaccinated against smallpox as far back as 40 years ago have some protection against monkeypox.

The same does not happen with the younger age group, who did not receive this immunizing agent in childhood.

It is not by chance that the vast majority of cases recorded in recent weeks have affected precisely individuals who have not yet reached the fourth decade of life.

In an article published in the journal Nature, epidemiologist Raina MacIntyre, from the University of New South Wales, Australia, explains that “every year since the eradication of smallpox, the population with little or no immunity against this group of viruses [os orthopoxvirus] only increased”.

It may therefore be that the number of individuals vulnerable to these infectious agents has become sufficiently high that an outbreak of international proportions becomes possible.

cascading action

Finally, it is no exaggeration to think that all these factors, together with a good dose of chance, may have contributed to monkeypox becoming a global problem.

In other words: although there is still no consensus on the causes of the public health emergency, low immunity, the return of agglomerations, the pattern of transmission and neglect of the virus help to understand and assemble this complex puzzle.

“But we still need to better understand everything that is happening,” summarizes Dal Ben.

If the picture is considered nebulous, there is greater clarity on what can be done to decrease the likelihood of infection with this virus.

The first step is to avoid the most risky situations, stay tuned for symptoms and seek medical evaluation if they appear.

“Any lesion that starts with an edema or a small redness and evolves into a plaque, has liquid, forms a wound and crusts, can be monkeypox”, describes Barbosa, who is also a professor at the Universidade Estadual Paulista (Unesp).

These manifestations can appear on the anus, genitals, face and hands.

“The lesion can also be acne, herpes, shingles or a number of other things. But when in doubt, it is important to seek medical attention and get tested”, he adds.

If the exam confirms the presence of this infectious agent, health professionals recommend isolation and avoiding close contact with other people until the wounds are completely healed (even their crust still carries the virus).

By limiting interaction and sharing of personal items, the patient reduces the risk of passing monkeypox forward and prevents the creation of new chains of contagion in the community.

Although the profile of infected people so far has focused on gays, bisexuals and men who have sex with men, the trend is for the disease to affect more and more people from other groups – this, by the way, is the natural and expected evolution of this outbreak. , according to experts interviewed by BBC News Brasil.

Still speaking of prevention, some countries such as the United Kingdom, Spain and the United States have already started vaccination campaigns against monkeypox, but there is still no forecast of when the first doses should arrive in Brazil.

For now, it is unclear whether condoms help protect against this virus – although condom use remains paramount in preventing the transmission of various sexually transmitted infections (STIs) such as HIV, syphilis, gonorrhea and some hepatitis.

In most cases of monkeypox, the condition progresses well and the patient is completely recovered in two to four weeks.

Deaths from this disease are considered rare by health authorities.

According to the portal Our World In Data, the world has already recorded 23,200 cases of monkeypox. Of these, 1,300 were diagnosed in Brazil.

This text was originally published in https://www.bbc.com/portuguese/internacional-62398486