The United States is experiencing a late-summer COVID-19 wave, with federal health data and monitoring programs showing rising infections across most of the country after a prolonged seasonal lull, according to the U.S. Centers for Disease Control and Prevention and independent tracking networks.
National Infection Trends and CDC Estimates
As of September 9, CDC estimates indicate that COVID-19 infections are growing or likely growing in 35 states, remaining stable in seven states, and declining in eight states, according to coverage by TODAY. Earlier estimates from August pointed to growth in as many as 47 states, led primarily by the South and West, according to Dr. Syra Madad, an infectious disease epidemiologist at Harvard’s Belfer Center and chief biopreparedness officer for New York City’s public hospitals, as reported by USA TODAY.
Despite the widespread geographic spread, national COVID-19 activity is still considered low overall by the CDC. During the week ending August 29, approximately 6% of COVID-19 tests returned positive results nationwide, compared to a 12% test positivity rate during the same period in 2025, according to CDC data cited by TODAY.
Wastewater Monitoring and Regional Hotspots
Wastewater surveillance data reveals a more pronounced viral presence than traditional clinical testing capture. WastewaterSCAN, an infectious disease monitoring program led by Stanford University, reports that SARS-CoV-2 activity is currently in the “high” category nationwide, showing a significant upward trajectory over a 21-day window.
“We’ve been seeing a pretty steady increase since late June across the (U.S.),” Amanda Bidwell, WastewaterSCAN Scientific Program Manager, told TODAY. By late August, SARS-CoV-2 concentrations in wastewater had surged 140% compared to July figures, following a pattern where concentrations have doubled each month since June, according to USA TODAY.
In the West and South, current wastewater viral concentrations have surpassed the peak levels observed during the 2025–2026 winter peak, according to Bidwell. State-level CDC data identify California, Nevada, and Texas as reporting the highest levels of coronavirus detected in wastewater. Meanwhile, an analysis published September 7 by the Pandemic Mitigation Collaborative’s data tracker, led by Tulane University assistant professor Michael Hoerger, Ph.D., indicated that at least 33 states and territories were experiencing active COVID outbreaks.
Understanding the Seasonal Wave Pattern
Health experts emphasize that the current upward trend is not unexpected, as SARS-CoV-2 has settled into a distinct pattern of biannual surges in the United States since the pandemic began.
“We’ve had two waves (every year). One in the middle to late summer, and the other during the winter,” Dr. William Schaffner, an infectious disease specialist and professor of medicine at Vanderbilt University Medical Center, told TODAY. Dr. Michael Mina, chief medical officer at Invivyd and a former assistant professor at the Harvard T.H. Chan School of Public Health, noted to USA TODAY that the national upswing begins consistently between early and mid-July each year.
Drivers behind the summer surge involve a mix of environmental and behavioral factors, including population contact rates and human aggregation indoors in air-conditioned spaces during periods of extreme heat, according to Mina. The arrival of the late-summer period also coincides with the return to school, which increases contact among groups and facilitates transmission as children return to classrooms, according to reporting by TODAY and USA TODAY.
While the wave has prompted localized disruptions—such as the San Perlita Independent School District in south Texas temporarily closing from August 25 to 26 to protect student and staff health—experts note that current viral concentrations and severity metrics remain lower than the intense summer surge driven by the “Stratus” variant in 2025.
Worth a look