The U.S. is in the midst of what has become an annual summer surge in COVID cases. In fact, the nation is experiencing its biggest spike in summer infections yet, according to test positivity records from the Centers for Disease Control and Prevention (CDC). Over the past four summers, peak test positivity has volleyed between July and August:

• 2020: 7.5% week ended July 11
• 2021: 11.2% week ended Aug. 21
• 2022: 14.3% week ended July 23
• 2023: 14.5% week ended Aug. 26

This year, cases have consistently increased since May, with test positivity projected to reach 18.1% the week ended Aug. 10. Provided the CDC confirms this preliminary statistic, it would mark the first time in more than two and a half years that test positivity has exceeded 16%. Even that may be an underestimate; with at-home COVID tests widely available, not everyone who tests positive reports their infection to their state health department.

So if you’ve noticed people masking up in crowded settings, testing kits in high demand at your local pharmacy, and colleagues calling out sick, you haven’t succumbed to a time slip back to 2020. COVID-related hospitalizations were projected to dip the week ended Aug. 10, having risen since late spring. Deaths, too, were projected to decline after increasing much of the summer. The percentage of emergency room visits involving a COVID diagnosis, however, continued their net climb.

All this, yet the coronavirus is no longer a pandemic. The U.S. public health emergency ended in May 2023, days after the World Health Organization said the virus “no longer constitutes a public health emergency of international concern.” COVID has shifted to become endemic, according to the CDC, meaning it’s a disease that, like the flu, is always present in a population. Dr. Donald Dumford, an infectious disease specialist at Cleveland Clinic Akron General, tells Fortune the surge pattern seems to repeat every six months.

COVID infections highest in South Central states

Travel is a driver of infection spread, and summer is primetime for globe-trotting. This spring, Tripadvisor’s 2024 Summer Travel Index showed 95% of respondents were planning to travel as much or more than they did last summer. Their top domestic destination? Las Vegas—located in a part of the country where COVID test positivity is now high.

In the four-week period ended Aug. 10, the national test positivity rate was 15.6%. During that time, five states in the South Central U.S. saw the highest test positivity, 21%. These states collectively make up the CDC’s Region 6:

• Arkansas
• Louisiana
• New Mexico
• Oklahoma
• Texas

States in Region 9—Arizona, California, Hawaii, and Nevada—had the next-highest four-week positivity rate, 18.8%. Ten other states across two Midwestern regions were also above the national average. No state—as well as the District of Columbia, Puerto Rico, and the Virgin Islands—had a positivity rate below 10%.

While in mid-August summer vacation is over for some, countless school districts don’t resume classes until September, and other travelers have jet setting yet to do before fall arrives. Dumford advises adequate sleep, hydration, and nutrition to keep yourself healthy on the road. If you’re journeying in close quarters, you may consider revisiting the public health habits you picked up in the early days of the pandemic.

“For those who are traveling, consider wearing a well-fitting mask while in the airport and while flying,” Dumford told Fortune last week. “This is my particular strategy, just figuring that it is a time when I am exposed to a large group of people—with the chance that some may be choosing to fly while ill because they already had a trip planned that they spent a lot of money on.”

This latest COVID surge may lose steam in the fall when the 2024–25 vaccines, manufactured by Pfizer, Moderna, and Novavax, become available. The CDC recommends vaccination for everyone 6 months and older; if you’re 65 or older or have a compromised immune system, ask your doctor if you’re eligible for additional vaccine doses.

For more on COVID-19:

• New COVID vaccines are here. What to know about 2024–25 shots as summer surge continues
• Will the XEC COVID variant bring a fall wave of infections? What to know about symptoms and spread
• COVID can cause mental illness—but being vaccinated helps, new study shows
• The summer COVID surge has arrived. Here’s the latest on symptoms and treatment