The spread in West Africa could also indicate that the virus appeared in a new animal reservoir. A whole range of animals can be infected with the virus – in addition to many rodents, monkeys, pigs and anteaters. Infected animals transmit the virus to other species and to humans with relative ease – as happened in the first outbreak outside of Africa. In 2003, the virus entered the United States with African rodents; these in turn infected prairie dogs, which were sold as pets. At least 47 people became infected with monkeypox.
On the Trail of Smallpox
Perhaps the most important factor, however, is that population-wide immunization coverage against smallpox is declining worldwide. Vaccination against smallpox reduces the likelihood of contracting monkeypox by around 85 percent. However, since the end of the vaccination campaign, the proportion of those who have not been vaccinated has increased continuously, making it easier for monkeypox to also infect humans. The proportion of human-to-human transmissions in all infections has risen from around one third in the 1980s to three quarters in 2007. The fact that the average age of those infected increases the longer the vaccination campaign is in the past also speaks for an influence of the vaccinations.
In view of these trends, African experts in particular warn that monkeypox could develop from a regional zoonosis to a globally relevant infectious disease. The virus may occupy the ecological and immunological niche that smallpox once occupied, wrote a team led by Malachy Ifeanyi Okeke from the American University of Nigeria in a 2020 publication.
“There is currently no global system to control the spread of monkeypox,” Nigerian virologist Oyewale Tomori said in an interview with The Conversation magazine. However, it is very unlikely that the outbreak in Great Britain will become an epidemic. According to the UKHSA, the risk to the population has been low so far. The authority is now looking for other cases and is working with partners internationally to find out whether there are similar clusters of monkeypox in other countries.