SARS-CoV-2, influenza, and other seasonal viruses: Northern and Southern Hemisphere perspectives

During the COVID-19 pandemic, the circulation of respiratory viruses changed dramatically, with only very low influenza activity observed in 2020-2021 compared to previous seasons. However, testing for these respiratory viruses remains important for managing hospitalized patients while the ongoing surveillance of these viruses is key for global public health.

This on-demand SelectScience^® webinar discusses the significance of other respiratory viruses in the context of the COVID-19 pandemic in the Northern and Southern hemispheres. Two leading experts in the field, Dr. Georgia Gioula and Dra. Mariela Muñoz Ortega, provide their opinions on testing approaches, surveillance programs, and what we might expect in the future.

Read on for highlights from the live Q&A session or register to watch the webinar at a time that suits you.

What viruses are important to look for in a multiplex test? If we had to choose three or four, what should we choose?

GG: If it’s during seasonal influenza season, it is important to detect for both SARS-CoV-2 and influenza viruses at the same time. This means that we can use a multiplex PCR assay to detect these two virus strains. But if we had to add one or two more viruses, I would say that respiratory syncytial virus (RSV) is an important virus to look for as well.

We have to keep in mind that we have to have patience with lower respiratory infections and probably younger patients. I think the symptoms are really important in order to decide which virus we're going to choose.

Are there specific patient populations that you would recommend testing for RSV together with SARS-CoV-2 and influenza?

GG: I believe that in children under five years old and elderly people, it's very important to do this kind of test. There are more risk factors in these groups.

For the upcoming flu season, would you recommend using a reflex approach, for example, SARS-CoV-2 first and then influenza, or would you recommend testing all symptomatic patients for both pathogens?

GG: It is very critical whether it’s during the influenza season. If it’s during the influenza season, the CDC and WHO insist on checking these viruses at the same time. But if it’s not during influenza season, then we might first test for SARS-CoV-2 and probably other respiratory viruses that circulate during this season instead of influenza.

The southern U.S. is seeing an increase in inter-seasonal RSV. What is the experience of Europe and South America currently with RSV?

GG: I can speak for Europe. There were some detections of RSV during last season. RSV hasn't disappeared as flu did, but these detections were in very low proportions. If we look past six seasons, we see that RSV is in very low numbers as well, but at least was still present, but flu has disappeared.

MO: In South America, in Chile specifically, during the last year, 2020, there were very few cases of RSV. This year, to date, there is a lag, but it's increasing. I believe this year we will have more cases of RSV than last year, but it's still so little compared to before.

Is there competition between the influenza viruses and SARS-CoV-2 within a host? If someone had both, what would happen?

GG: I think we have to wait and see what will happen because actually, we had very, very low coinfections with SARS-CoV-2 and influenza viruses. We don't still know who the winner will be. I think next winter we're going to answer these questions, we're going to see more coinfections and probably we'll see which is going to be the dominant virus strain when a person is infected.

MO: I agree with Georgia, because there are so few cases of coinfection in my country about 25% of coinfection. It’s too low for us to reach any conclusions.

Is there any correlation with COVID-19 cases and the seasons or weather?

MO: Yes, in South America, July is the coldest month. There are always more cases of any respiratory viruses in that month, due to the temperature. It's colder, people live in closed spaces, and that propels the infection.

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