Animal-spread infections that are increasing exponentially

Four types of zoonotic Infections have been increasing at an exponential rate, researchers warn today.

Work by researchers at US-based biotechnology firm Ginkgo Bioworks, Emeryville, California, shows that based on current trends, those viral pathogens – Filoviruses, SARS Coronavirus 1, Nipah virus, and Machupo virus – are collectively set to kill 12 times as many people in 2050 as they did in 2020.

Whilst three of the viruses have been associated with animals such as bats and pigs, the Machupo spread through a large species of mice in South America.

Writing in BMJ Global Health, the researchers warn climate and land use changes will drive the frequency of spillover events, facilitated by population density and connectivity, but they add the implications for future global health are difficult to characterise, given limited historical data on the annual frequency and severity of zoonotic spillover over time.

The team drew on their own epidemiological database, including World Health Organization in the form of Disease Outbreak News reports; outbreaks caused by a viral pathogen that killed 50 or more people; and historically significant outbreaks, such as the 1918 and 1957 flu pandemics, to spot trends in spillover events that might shed light on future expected patterns.

They looked at more than 3150 outbreaks and epidemics between 1963 and 2019 to analyse time trends in the number of outbreaks and associated deaths caused by these viral pathogens.

From this, they identified 75 spillover events in 24 countries during this period, which caused 17,232 deaths. Of those, 15,771 in 40 outbreaks were caused by Filoviruses, mostly in Africa.

The number of spillover events and reported deaths attributable to these four groups of viruses have increased by almost 5% and 9%, respectively, every year between 1963 and 2019.

“If these annual rates of increase continue, we would expect the analysed pathogens to cause four times the number of spillover events and 12 times the number of deaths in 2050 than in 2020,” they write.

They add: “Our evaluation of the historical evidence suggests that the series of recent epidemics sparked by zoonotic spillover are not an aberration or random cluster but follow a multi-decade trend in which spillover-driven epidemics have become both larger and more frequent.

“The ultimate package of measures to support global prevention, preparedness, and resilience is not yet clear. What is clear, however, from the historical trends, is that urgent action is needed to address a large and growing risk to global health.”

Meadows AJ, Stephenson N, Madhav NK et al. Historical trends demonstrate a pattern of increasingly frequent and severe spillover events of high-consequence zoonotic viruses. BMJ Global Health 3 November 2024; doi 10.1136/bmjgh-2023-012026


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