When COVID arrived in the US in 2020, many of us thought COVID would be a winter illness. The US is used to respiratory illnesses peaking in the winter since that’s the pattern that flu and RSV follow. And as expected, there’s generally been a winter surge in COVID cases and hospitalizations each year. But then, every year since 2020, the US has also experienced a summer surge peaking in July and August.
There are several possible reasons for COVID’s summer surges. Many think that the summer surge happens because people stay indoors in air-conditioned spaces with closed windows to beat the summer heat, which can increase transmission due to lack of ventilation. Another potential reason is because people travel more in the summer, creating more opportunities for COVID to spread between populations. There is also generally a higher number of COVID cases in COVID’s “off-season” than for the flu. The higher number of summer COVID cases means that it is more likely for a surge to occur.
So far this year, we’ve experienced a small winter wave of COVID. That raises a question: Will COVID have a summer wave that’s bigger than its winter wave this year? Now that COVID has been around for 5 years, will summer turn out to be its favorite season?
The way we get the answer about COVID’s seasonal trends is through public health surveillance data. The word “surveillance” might make you think of international spy agencies, but in public health, surveillance refers to the monitoring of disease patterns through constant collection and interpretation of data about the disease. Public health surveillance helps us understand where a disease is spreading, tells us how much of our health care system’s resources are being used to fight the disease, and gives us clues on what a disease may look like in the future. All this information helps us better understand diseases and, in turn, better overcome them.
This summer we’ll be following the US’s COVID surveillance data to see if there is a summer surge again. There are several COVID surveillance systems in the US tracking things including COVID emergency department visits, hospitalizations, and deaths. All these national surveillance systems’ data are publicly available and updated regularly on the CDC’s website. CDC coordinates these national surveillance systems in collaboration with participating hospitals and other health care facilities across the country. Each surveillance system includes a group of facilities that paints a picture of disease patterns nationally. These surveillance activities are a key tool in keeping America healthy, and they’re unfortunately threatened by public health funding cuts.
If you’re curious to follow COVID trends over the summer, make sure to check out the CDC’s COVID Data Tracker webpage. The COVID Data Tracker has links to all kinds of different surveillance data like the COVID-NET hospitalizations surveillance system, the RESP-NET hospitalizations surveillance system combining flu/COVID/RSV data, and the flu/COVID/RSV emergency department visit data from the National Syndromic Surveillance Program.