A newly compiled catalogue of viruses that infect humans identifies those with the highest potential to spark the next global health emergency. Researchers have created the most extensive list of known RNA viruses capable of infecting people, aiming to help governments and health agencies prioritize surveillance and preparedness efforts.
The catalogue highlights several viruses as high on the watch list, including avian influenza (bird flu) and SARS-like coronaviruses. Bird flu is a particular concern due to its continued evolution in wild birds and its ability to infect poultry, mammals, and humans, increasing opportunities for adaptation. While human-to-human transmission of bird flu is currently rare, scientists worry about its potential to acquire this capability.
Another significant threat identified is the potential for new viruses related to measles to cause a pandemic. Measles is already highly contagious, and a strain capable of spreading easily among humans could lead to a widespread emergency. Coronaviruses also remain a concern, with COVID-19 demonstrating their capacity to quickly develop efficient human transmission. The emergence of another SARS-like coronavirus from wildlife is considered a realistic future scenario.
Other viruses under close monitoring include Nipah virus, Ebola virus, and Marburg virus. These viruses have caused deadly outbreaks and demonstrate some ability to spread between people. Nipah virus has a high fatality rate, between 40% and 75%, while Ebola and Marburg viruses are even more lethal, with fatality rates ranging from approximately 25% to 90% for Ebola and 24% to 88% for Marburg. However, their limited human-to-human transmission and tendency to cause rapid, severe illness make them less likely to initiate a global pandemic compared to viruses like influenza or coronaviruses that can spread before symptoms are severe.
Professor Mark Woolhouse, an infectious disease epidemiologist at the University of Edinburgh, explained that many newly discovered viruses that spill over from animals are unlikely to cause pandemics because they cannot sustain human-to-human transmission. The greatest danger, he argues, comes from viruses that have already overcome some biological hurdles for human-to-human spread. He noted that this data can also help predict the characteristics of future pandemic viruses, sometimes referred to as Disease X.
The catalogue identifies 239 known RNA virus species that infect humans, out of potentially millions of RNA virus species worldwide. The research aims to provide clarity on which of these viruses pose the greatest risk, enabling a more focused approach to pandemic prevention and response.
While viruses like Ebola and Marburg are extremely deadly, their rapid onset of severe symptoms makes infected individuals easier to identify and isolate, thus limiting their pandemic potential. Conversely, viruses that can spread asymptomatically or with mild initial symptoms, such as certain influenza strains or coronaviruses, present a greater risk for widespread transmission.