(NEXSTAR) -- Pertussis, a disease commonly referred to as whooping cough, is spreading quickly, the Centers for Disease Control and Prevention warns. The U.S. has seen five times more cases in 2024 than we did at this time last year. In California, at least 1,744 cases have been reported this year. Twenty percent of those are traced back to one Bay Area county: Marin. While Marin isn't one of the most populated California counties, it has the second-most cases of whooping cough in the state, according to the latest available data from the California Department of Public Health. The only county with more cases is San Diego. Marin health officials said they've investigated 355 cases of whooping cough so far. Experts warn the case count will continue to rise if people aren't careful. The disease is highly contagious and can spread quickly through schools, childcare centers and over large areas. It spreads easily from person to person as people cough, and sickened people can be contagious for weeks. Deadly E. coli outbreak linked to organic carrots sold in multiple states Experts believe the 2024 surge in cases may be in part because of missed vaccinations during the COVID-19 pandemic. Widespread masking in 2020 and 2021 also helped prevent spreading of the bacteria that causes pertussis. Now, the disease is back with a vengeance, and we're seeing more cases than we did in 2019. Marin saw fewer than 30 cases every year for the past five years. In 2021, zero were reported. There are signs things may be starting to get better, Marin Health and Human Services said, with fewer cases since September. The number of pertussis cases around the Bay Area, as of Sept. 30 (the latest publicly available data from CDPH), are: Alameda County: 35 cases Contra Costa County: 109 cases Marin County: 336 cases (though local officials report more since then) Napa County: 13 cases The City and County of San Francisco: 84 cases San Mateo County: 54 cases Santa Clara County: 39 cases Solano County: 6 cases Sonoma County: 65 cases What are the symptoms of pertussis/whooping cough? As its nickname suggests, the disease’s main symptom is a bad cough, followed by a “high-pitched intake of breath that sounds like ‘whoop,'” the Mayo Clinic explains. The onset of symptoms can look a lot like the common cold. People report having congestion, a runny nose, watery eyes, fever, and a cough. But if the symptoms are persistent and start to worsen after a week or two, it may be whooping cough. “Thick mucus accumulates inside your airways, causing uncontrollable coughing,” the Mayo Clinic says. Young babies, who are especially vulnerable to complications from pertussis, may not cough at all. “Instead, they may have apnea (life-threatening pauses in breathing). The apnea may cause cyanosis (to turn blue) or they may struggle to breathe,” the CDC says. Why you should throw away your black plastic cooking utensils How is whooping cough treated? While many people can recover on their own, whooping cough can be treated with the help of antibiotics. Vaccines can also help prevent getting sick with pertussis in the first place. While the vaccines are highly effective, they wear off, so the CDC recommends making sure you’re up to date. Babies need to be vaccinated at 2 months, 4 months and 6 months. Kids need two booster shots – one between the ages of 15 and 18 months, the other between 4 and 6 years old. Preteens should get a booster between 11 and 12 years old, too. The CDC also recommends adults get vaccinated if they’ve never had a dose.