When researchers make predictions about how viruses spread, they often assume everyone in a population is equally likely to get sick. But, that’s not the case, according to a study in PLOS Pathogens in February by Seema Lakdawala, associate professor in Pitt’s Department of Microbiology and Molecular Genetics. Lakdawala and her team found that viruses like influenza generate varying immune system responses, and immunity to one virus can protect against other viral infections. They also discovered that a child’s first influenza infection influences their immunity to future flu viruses. In the study, Lakdawala and her team used ferret models, which have a similar susceptibility and immune response to flu as humans.

Why are these findings important?

Different prior infections can shape susceptibility.

What are the implications for how we approach and treat infections?

We’re starting to think more about personalized medicine. You could imagine a scenario where understanding the age and birth year of an individual and what they were first infected with in their immune history could shape what they’re likely to be infected with. That impacts pandemic emergence. It’s all related.

What can this study tell us about COVID-19 and future pandemics?

We think it will help inform studies looking at how pre-existing infections with human coronaviruses influence transmission or susceptibility to SARS-CoV-2. There was talk early [in the pandemic] that kids were less susceptible to COVID-19 because of their prior experience with human common-cold causing coronaviruses. I think there are a lot of parallels when we think about pandemics and respiratory viruses.

You are a flu expert, but can you tell us if you think that talk was right—that kids were less susceptible to COVID-19 because of their immune histories?

We’ve learned that kids can become infected with SARS-CoV-2 but, luckily, many don’t develop severe disease. However, we’ve observed the rates of infections in children increasing and, with emerging variants, like delta, infection rates are increasing and disease severity is worsening in kids. Whether the initial low disease burden in kids is due to prior immunity with [other] coronaviruses is still unclear, but it’s something my lab is researching with our collaborators.