COVID-19 will become a seasonal disease, U-M epidemiologist says

Reviewed by Emily Henderson, B.Sc.Sep 22 2021

A University of Michigan epidemiologist believes that COVID-19 will become a seasonal disease, likely in the fall and winter seasons.

Rafael Meza, professor of epidemiology and global public health at the U-M School of Public Health, draws a parallel between the reality in the United States, Brazil and other South American countries, mainly regarding vaccination.

Some South American countries, including Brazil, are experiencing a downward trend in the number of cases and deaths of COVID-19 in recent weeks. Despite this data, experts say it is not time to relax. What should the pandemic scenario be in the region in the coming weeks?

Given the high number of people who already have had a COVID infection and the considerable number of people with at least one vaccine dose, we hope cases will continue to decrease in the coming weeks. In addition, the fact that Brazil and the rest of South America are heading into the spring and summer provides some optimism that COVID cases could remain low in the region as people can engage in plenty of outdoor activities, limiting indoor contact.

That being said, the looming threat of the Delta variant should give us pause as there is a latent possibility of new outbreaks and breakthrough infections, particularly in areas with low levels of vaccination and immunity.

Even with the advance of vaccination, could this downward trend be reversed in the coming weeks due to Delta and the relaxation of restrictions?

This is plausible. The U.S., Canada, Mexico and the U.K. are examples that even with relatively high vaccination levels, particularly in Canada and the U.K., Delta can cause a resurgence in cases as restrictions are lifted.

I think that this is a reality that all countries need to face. But clearly, countries with high levels of vaccination and preexisting immunity due to previous infections do better in terms of hospitalizations and deaths, even if cases increase, such as Canada and the U.K., compared with the U.S.

With COVID rates dropping and vaccinations rising, how important is it to keep the mask mandates?

In the U.S., a considerable portion of the population used masks because they were mandated locally (we never had a federal mandate). So once the mandates were lifted, many of those individuals immediately stopped wearing masks, regardless of their vaccination status. In contrast, others have continued using masks in public settings and closed indoor spaces. But it might be a small minority in certain areas in the U.S.

In Latin America, things might be a little different, with considerable numbers of individuals using masks because they believe they can protect themselves and others. As such, they might continue wearing masks in certain situations.

Here is where public health leaders and organizations could play a critical role in advising the population about the benefits of mask use. They should also explain the situations where they are most helpful, for example, when riding a bus or public transportation, so that individuals can make the best decisions independently of the end of mask mandates.

Is it possible to draw a parallel between South America and the United States regarding the pandemic?

There are certainly some parallels. In most countries, we have seen these waves of cases, hospitalizations and deaths, which are then followed by periods of relative calm. As time progresses, it is expected that COVID will turn into a seasonal phenomenon, like influenza. It will probably follow a similar pattern as other respiratory viruses, which cause epidemics predominantly during fall and winter, but have low activity during spring and summer, at least in the Northern and Southern hemispheres.

Many experts believe that after this fall and winter, and once we are done with Delta outbreaks, we’ll move toward a seasonal pattern of COVID-19 epidemics in the U.S. It is conceivable that a similar pattern could emerge in Brazil and the rest of South America, where cases might remain low in the next few spring and summer months, to come back up again in fall and winter.

In South America, Brazil currently stands out as the focus of COVID-19. Is the country at greater risk than its neighbors, even with the discovery of the Mu variant in Colombia?

I think one thing that we should all now have clear is that we are all connected and that everything that happens in one country regarding COVID will likely affect what happens in the rest. Countries with high levels of cases become sources of outbreaks in other countries and of new variants, which affect everyone.

I think that Brazil has had a challenging time with COVID in part because of its geographical and geopolitical prominence, its large population and area size, and its complex social and political structure. I also think that the significant economic and social disparities and the problematic political climate have made Brazil particularly susceptible to COVID. But similar things could be said of other countries in the region. In the end, this is a global pandemic and all nations will experience outbreaks and multiple waves until we settle into a seasonal pattern or, if we are so lucky, it goes away.