DeKalb, Ill. — Amid the busy transition to remote teaching, NIU faculty members also have pivoted aspects…
DeKalb, Ill. — NIU Biological Sciences Professor Neil Blackstone says evolutionary theory can provide important insights into the future course of the COVID-19 pandemic—on topics ranging from future research directions to the potential efficacy of future vaccines.
Blackstone recently wrote a commentary on the topic published in the academic journal, Evolution. His co-authors are his daughter, Sarah Blackstone, an assistant professor of health sciences at James Madison University, and wife, Anne T. Berg, a research professor at the Epilepsy Center, Ann & Robert H. Lurie Children’s Hospital of Chicago.
“It is imperative to consider the potential effects of evolution when considering a newly emerged and rapidly evolving pathogen,” the authors write. “Evolutionary theory provides predictions to guide scientific investigations as well as public health policy.”
Blackstone’s area of expertise is evolutionary conflict, or the study of competing forces at play in evolution. Like people, viruses evolve and are subject to natural selection. Unlike people, viruses can evolve rapidly.
In his commentary and a subsequent interview, Blackstone provides some key takeaways:
- More research is needed on the differences among strains, or genetic variants, of SARS-CoV-2, the virus that causes COVID-19.
Scientists know the virus has mutated. “It’s a slow-mutating virus, but it’s been replicated an uncounted number of times, so we know there must be variation,” Blackstone says. “Without a doubt, there are many strains.”
If mutations are beneficial to the virus’s survival, the mutated virus is more likely to reproduce itself. Different strains could be more or less lethal or infectious, but there hasn’t yet been a wealth of research conducted on potential differences, Blackstone says. “The big question is, ‘Are there functional differences among the strains?’ ” he adds.
Some evidence suggests that might be the case—with less-pathogenic strains causing mild or inapparent infections and more virulent strains causing more severe disease. Blackstone points to the case of the Diamond Princess cruise ship. About 700 passengers were infected with the virus, but it had a relatively low case fatality rate, possibly reflecting an initial infection with a mild strain.
A better understanding of potential functional differences among virus strains might be needed to guide development of treatments and vaccines.
- A vaccine made with one strain might confer limited immunity to other strains.
If there are not substantial differences among strains, one vaccine might be effective against SARS-CoV-2. However, if there are indeed substantial differences, a vaccine that works on one strain might not work as well on another—and we might end up combatting COVID-19 for years, Blackstone says. As with seasonal influenza, newly formulated vaccines might be needed annually.
The genetic variation among strains also could lead to the rapid evolution of resistance to therapies that treat the disease, he says. A case in point would be HIV, which became resistant to azidothymidine (AZT). For this reason, Blackstone says evolution of resistance should be considered as treatments are being developed.
- High population density and other circumstances that favor rapid transmission might also favor more deadly strains.
Blackstone says an evolutionary theory called “multilevel selection” would suggest that crowding of people—such as in large cities, multi-generational homes and nursing homes—favors more pathogenic strains of SARS-CoV-2 and predicts more severe disease.
“Rapid transmission facilitates pathogenicity,” or the disease-producing capability of the virus, Blackstone says. “One of the things that facilitates rapid transmission is high density.”
That might have been one of the reasons why hospitals in some large cities across the country were overrun during the early phases of the pandemic, when fewer public health measures were in place and a rapidly spreading virus had ample opportunity to proliferate. Slower-replicating and less-pathogenic strains might have been present as well in the early stages, Blackstone says, but they were not favored by natural selection as long as the more-rapidly spreading virus had ample opportunity to thrive.
- People can favorably change the evolutionary course of the disease.
The good news, Blackstone says, is that public health measures enacted as the pandemic has continued—such as wearing of face masks, social distancing and isolation of people who are sick—are designed to counteract crowding and might also help beat back more-lethal virus strains.
“Above all, we want to lower the transmission rate to channel the predominance of a less-pathogenic virus,” Blackstone says. “You can channel evolution in a way favorable to human society.”
- Hospital workers might be at greater risk, simply because they’re exposed to more-pathogenic virus strains.
Blackstone says this makes common sense. People who are hospitalized, especially those who did not have pre-existing conditions, are more likely to have been infected by severe strains. Consequently, healthy health care workers who are routinely exposed to these pathogenic strains might be at greater risk for infection.
- Priority might be focused on testing and contact-tracing the most seriously symptomatic patients.
Testing and tracing contacts of individuals with severe disease would be most likely to identify those at greatest risk of contracting a severe infection, Blackstone says. However, that doesn’t mean that mild cases can be ignored. Mild strains that are rapidly transmitted have the potential to evolve and become more pathogenic.
- As human society occupies more and more of the planet, parasites are more likely to invade human-related niches—such as human beings themselves along with agricultural crops and livestock.
Why do new human diseases keep popping up? Likely, it’s because the human population and our crops and livestock simply dominate the biosphere. Blackstone says that means there is a bright future for human parasites, compared to a not-so-bright future for, say, polar or panda bear parasites.
Media Contact: Tom Parisi
Northern Illinois University is a student-centered, nationally recognized public research university, with expertise that benefits its region and spans the globe in a wide variety of fields, including the sciences, humanities, arts, business, engineering, education, health and law. Through its main campus in DeKalb, Illinois, and education centers for students and working professionals in Chicago, Hoffman Estates, Naperville, Oregon and Rockford, NIU offers more than 100 areas of study while serving a diverse and international student body.