A recent analysis of monkeypox infections in a remote part of the Democratic Republic of the Congo (DRC) with a strain associated with a more severe disease than what’s circulating worldwide reveals that transmission rates are increasingly closer to the point where outbreaks would be larger and more frequent.
Researchers from the U.S. Centers for Disease Control and Prevention (CDC), Kinshasa School of Public Health, and the DRC’s Ministry of Public Health put together the report, which is based on data from 2013 to 2017. It raises new concerns about how monkeypox is still a big problem in Africa, even though it hasn’t been given much attention. That includes the possibility that it will spread and cause more cases in African communities, which might raise worldwide outbreak risks. The results were shown today at the American Society of Tropical Medicine and Hygiene’s Annual Meeting.
The results of the study, according to the CDC fellow Kelly Charniga, reveal “that monkeypox transmission in the area we studied was notably higher than previous estimates and was getting close to the point where it can cause large and sustained local outbreaks.”
“With today’s interconnected world,” she adds, “outbreaks don’t necessarily stay at their source. This research puts the global health community on alert that there may be the opportunity for larger outbreaks in DRC on the horizon and we must work diligently to prevent future outbreaks where people are most at risk for getting and dying from monkeypox.”
Charniga and her colleagues looked at reports from 1,463 lab-confirmed cases that happened in Tshuapa Province in the northwest of the DRC between 2013 and 2017. The team’s main goal was to figure out the “reproduction number,” which is the average number of new cases that one infection causes.
The effective reproduction number, which is also called Rt, is a key parameter for any disease that can spread. Rt values above 1 show that each new infection is causing at least one more case, which means that the disease could keep spreading. Charniga and her team of researchers found that the Rt for monkeypox had gone up to 0.81 in the area they looked at. In the 1980s, that Rt value was between 0.3 and 0.5, which was in line with the small, random outbreaks of monkeypox that have been happening in the area for about 50 years.
“When it’s significantly below one,” according to the researchers, “outbreaks die out because fewer people are being infected – and thus spreading the disease to others.”
“That’s what we have typically seen in the DRC, small outbreaks that don’t last. But if it gets closer to or above one,” she warns, “then a disease can continue to spread between people in a region and outbreaks can be larger and more frequent.”
The study also uncovered further proof that monkeypox “spillovers” from rodents, the presumed natural reservoirs, to humans may occur with greater frequency than previously thought. Infections from rodents, which often affected children, then spread from person to person to other people in the same household. Charniga said the more this happens, the more monkeypox can spread between people.
Over the past several years, there has been an uptick in reports of monkeypox in nations across Africa where it is commonly prevalent. This includes the disease’s reappearance in Nigeria after a 40-year absence.
“Many people in CDC, the World Health Organization and in health ministries and research institutions across sub-Saharan Africa were calling attention to the rising danger of monkeypox long before we started seeing infections outside of Africa,” remarks ASTMH President Daniel Bausch, MD, MPH&TM, FASTMH.
“This study,” according to the ASTMH President, “provides important new insights that point to the urgent need to provide additional resources that can help Africans fight this disease.”
Dangerous strain threatens both local and global population
Another worry is that the monkeypox virus exists in two different kinds, or “clades.” Clade I, which has been going around for a long time in the DRC, can kill up to 10% of people. Clade II, which is found in West Africa and is the cause of recent outbreaks outside of Africa, kills less than 3% of people. Charniga said that serious problems caused by monkeypox, like blindness, seem to happen more often in Clade I.
Since smallpox vaccination was stopped in 1982 after global eradication, both clades of monkeypox have become increasingly frequent in Africa.
The monkeypox virus is a member of the same virus family as the variola virus, which causes smallpox; therefore, smallpox vaccines and treatments may also be effective against monkeypox. However, there is limited access to these products in Africa, as the majority of the global stock was manufactured as a bioterrorism countermeasure against smallpox and is not generally available. There is now an approved vaccination for monkeypox, but there is only one producer worldwide, and majority of its production is outsourced to the United States.
Given the limited availability of vaccines, combating monkeypox in Africa—and reducing the likelihood of new global outbreaks, including those involving the more serious Clade I—requires increased surveillance and contact tracing to prevent the disease’s spread. She said that since 2010, the CDC and the Kinshasa School of Public Health have been helping DRC improve surveillance in rural areas, where many clinics still use paper forms to report suspected cases.
“The best way to prevent monkeypox from causing more outbreaks in DRC and from becoming a bigger global problem,” according to her, “is to devote more attention to areas where it is clearly causing the most suffering today.”
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