Attendance at big-name summer music festivals — like Coachella, Lollapalooza, and Glastonbury — have skyrocketed in recent years, making these events among the most lucrative in the entertainment industry.

Music festivals are a known hotbed for excessive boozing, drugs, and casual hookups. But they’re also a hotbed for something else: diseases. Given that attendees are often sweaty, sleep-deprived, dehydrated, and grimy, it’s not exactly surprising that people are coming away from music festivals with something much worse than a week-long hangover.

Read on to find out what you’re risking.

1. Zika

Chicago-based Lollapaloza has been around since 1991, with its first-ever South American incarnation taking place in Chile in 2011. But just last year, this popular music festival’s first Colombian edition, which was set to take place in September, was cancelled after an unnamed headliner pulled out of the festival. At the time, rumor had it that that headliner was Rhianna, and Zika virus fears had spurred her to withdraw.

2. Norovirus

Also known as acute gastroenteritis, norovirus is actually a group of viruses that tend to cause nasty digestive system symptoms including vomiting and diarrhea. In the spring of 2014, the Health Center at California Polytechnic State University saw 27 cases of norovirus. Nearly all of the students had attended the Stagecoach Country Music Festival in Indio, California, while two had been in close contact with those who went. A nurse practitioner commented that it was possible that the virus had started at Coachella, which was held at the same venue only a week earlier.

3. Measles

Meanwhile in the U.K., Public Health England released a statement in August of 2016, just prior to the long-popular Glastonbury Music Festival. The statement warned attendees to make sure they were vaccinated against measles after the number of cases had more than quadrupled compared to the previous year, jumping from 54 to 234. Most of the cases were linked to festivals and other large public gatherings.

4. Hepatitis A

Rewind back to July 2003, when the Centers for Disease Control and Prevention reported an influx of hepatitis A cases related to “outdoor concert and camping events.” Though the report didn’t specify which festivals might have been responsible, they did say that “crowded conditions, a lack of hand-washing facilities, and poor sanitation” had likely contributed to the spread of hep A, which is transmitted when water or food that has come into contact with contaminated feces is ingested.

5. Influenza

“Festival flu,” as its widely known, hasn’t been documented by researchers, but according to those in the music festival industry, it’s very real. Lorena Cupcake, a writer and social media manager, looked back on a summer of festivals in 2016 only to realize she’d been sick for nearly two months straight after attending Mamby on the Beach, Pitchfork, and Lollapalooza one after another. Though festival-goers are less likely to come away with the flu — a common cold is more likely — that doesn’t mean that the influenza virus isn’t present. Not to mention, a perfect storm of factors, including poor hygiene, fatigue, and dehydration, make attendees more susceptible to falling sick.

6. Sexually Transmitted Diseases

Though outbreaks of common sexually transmitted diseases following music festivals are far more difficult to trace, in all likelihood, they're happening. According to a 2013 research paper published in one of Europe's foremost public health journals, "Sexual transmission of infectious diseases may also occur and is likely to be underestimated and underreported."

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