The Centers for Disease Control and Prevention (CDC) had preliminarily documented more than 17,600 whooping cough infections nationwide as of Oct. 5—more than four times the nearly 4,000 infections recorded at this time last year. So what’s causing the 342% increase?

The U.S. generally sees upward of 10,000 whooping cough infections each year, per the CDC, with more than 18,600 reported in 2019. But since 2020, when the COVID pandemic began, annual infections have barely surpassed 6,100 and reached a low of 2,100 in 2021.

While people wore masks to shield themselves from COVID, in doing so they also were protected from whooping cough transmission. Public health initiatives such as social distancing and remote work and school also helped keep outbreaks at bay.

Cumulative whooping cough cases have exceeded those recorded at this time in 2023 in all regions, including the U.S. territories. These states had the most cases the week of Sept. 29–Oct. 5:

• Ohio: 44
• New York (excluding NYC): 34
• Pennsylvania: 28
• Alaska: 25
• Virginia: 20

Though whooping cough cases peak every few years, outbreaks can be difficult to manage and identify because cases may go unreported, and infected people may confuse their symptoms for those of another bacterial or viral infection, the CDC says. Your doctor can confirm infection via blood test or mucus sample.

What is whooping cough?

A bacterium called Bordetella pertussis causes whooping cough, an upper respiratory disease formally known as pertussis. The nickname, according to the Mayo Clinic, comes from the high-pitched “whoop” sound many infected people make when they inhale following a coughing bout.

How does whooping cough spread?

Because particles containing Bordetella pertussis get released into the air when a sick person coughs or sneezes, the illness is highly contagious.

Whooping cough is , the CDC says, because some people may have only mild symptoms, not realizing they have the disease and unknowingly spreading it to others. You’re infectious as soon as symptoms appear, and you can sicken others up to two weeks after coughing begins.

While anyone can catch whooping cough, it’s most common in infants and young children who haven’t received all five doses of the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine. The CDC recommends children under 7 get the DTaP vaccine at these ages:

• 2 months
• 4 months
• 6 months
• 15–18 months
• 4–6 years

However, vaccine protection wanes over time, meaning adults and adolescents 11 and older are susceptible to whooping cough if they don’t receive the tetanus, diphtheria, and pertussis (Tdap) vaccine every 10 years. Expectant parents can help protect their babies from whooping cough by getting a Tdap shot between the 27th and 36th weeks of pregnancy.

What are the symptoms of whooping cough?

Whooping cough may bear cold-like symptoms, but they take five to 10 days to appear after exposure to Bordetella pertussis and may take up to three weeks to develop. The CDC breaks down common symptoms into two stages:

• Early symptoms (lasting 1–2 weeks)
  • Low-grade fever
  • Mild, occasional cough
  • Runny or stuffy nose
• Later symptoms (lasting 1–6 and up to 10 weeks)
  • Rapid, violent, and uncontrolled coughing fits that can cause people to:
    • Feel very tired after the fit, but usually seem well in between fits
    • Fracture a rib
    • Have difficulty sleeping at night
    • Make a high-pitched “whoop” when they inhale after a coughing fit
    • Struggle to breathe
    • Vomit during or after coughing fits

Infants may have breathing difficulties rather than a full-blown cough. Whooping cough can be deadly for babies, with one in three under a year old requiring hospitalization. Complications are possible in older children and adults, but infection tends to be less serious for them, especially if they’re vaccinated.

Your first instinct may be to treat symptoms with over-the-counter cough medicine, but the CDC instead recommends prescription antibiotics to help you recover more quickly and effectively.

For more on respiratory illnesses:

• Public health experts are warning of a ‘quad-demic’ this winter. Here’s where flu, COVID, RSV, and norovirus are spreading
• Yes, you can get the COVID, flu, and RSV vaccines at once. Here are the pros and cons
• RSV can be deadly, especially for older adults. What to know about symptoms and the new vaccine
• COVID sickens older adults most severely, but less than half say they’ll get the new vaccine
• Free, at-home COVID tests are back. Here’s how to order yours