Whooping cough — a highly contagious and potentially dangerous illness — has surged in California this year, staging a comeback to levels not seen since the start of the COVID-19 pandemic.
Across California, there were fewer than 300 reported cases of whooping cough, also known as pertussis, all of last year. This year, there were 1,744 reported cases statewide as of the end of September, according to the California Department of Public Health.
Those at highest risk from whooping cough are infants younger than 1 year old, according to the U.S. Centers for Disease Control and Prevention. Other people at higher risk of severe illness include those who are immunocompromised or who have moderate-to-severe asthma.
In Los Angeles County, there have been 347 confirmed and probable whooping cough cases so far this year, up from 126 reported in all of 2023 and more than quadruple the 2022 total.
Nationwide, the number of reported whooping cough cases in 2024 is higher than what was reported in 2019, the last year before the COVID-19 pandemic. In recent years, many common respiratory illnesses saw large declines in transmission — in part because of the preventive measures put in place to combat the coronavirus.
So far in 2024, the number of whooping cough cases in Los Angeles County is 3.5 times higher than at the same point last year.
“We’re definitely noticing that more and more schools are reporting several of their students having infection,” said Dr. Nava Yeganeh, medical director for Vaccine Preventable Disease Control for the L.A. County Department of Public Health. “We’re keeping a close eye on that and trying to make sure we can do whatever we can to decrease the number of pertussis cases.”
Whooping cough typically surges every three to five years. “So, we’re overdue,” Yeganeh said. “Our last big spike was in 2019. … We aren’t quite to where we were in 2019, so we’re grateful for that, but really keeping an eye on the numbers.”
Los Angeles County reported 1,691 confirmed, probable and suspected whooping cough cases in 2019.
One of California’s worst whooping cough seasons in recent memory was in 2010, when more than 9,000 cases were reported — the most in 60 years, according to the California Department of Public Health. Ten infants died from the disease that year. Four years later, more than 11,000 cases of whooping cough were reported across the state, and two infants died.
The last infant to die from whooping cough in L.A. County was in 2014.
Whooping cough can be a pernicious disease that starts out like a cold, but then takes a severe turn with coughing that persists for weeks or months, according to the CDC. An infected person’s cough contains contagious bacteria, which can be breathed in by anyone nearby.
People are contagious as soon as they feel sick and remain so for at least two weeks after they begin coughing. Antibiotics can help shorten the infectious period and reduce the rate of disease transmission.
Whooping cough is named for the high-pitched whoop that can be heard as patients suck in air after coughing. Some people describe whooping cough as producing the worst coughing fits they’ve ever experienced.
“It’s really hard to watch, because it looks like they can’t catch their breath,” Yeganeh said.
Those who have these symptoms should get tested and treated, and stay home to prevent spreading the disease.
Whooping cough can be devastating for infants. It’s possible for babies to not cough and instead suffer from apnea — pauses in breathing that threaten their lives, according to the CDC. The babies can turn blue as they struggle to breathe.
Infants can also suffer from something called pulmonary hypertension — when blood isn’t getting through the arteries en route to the lungs to pick up oxygen. The pertussis toxin can trigger a reaction that produces a high white blood cell count, Yeganeh said — potentially causing sludging in the blood vessels leading to the lungs.
“It takes a long time to reverse,” Yeganeh said.
Schoolchildren can also get very sick, she said, with coughing so severe they can’t sleep. And adults can sometimes cough so hard that they fracture their ribs.
There are vaccines for whooping cough. As early as 2 months old, babies get a formulation called DTaP, which besides pertussis also protects against diphtheria and tetanus. The whooping cough vaccine in a different vaccine formulation, called Tdap, is given to adolescents at age 11 or 12 and to adults every 10 years.
Additionally, starting in 2012, women were recommended to get a whooping cough vaccination during every pregnancy. Pregnant, vaccinated moms then pass protective antibodies to their babies.
Also, everyone who is caring for infants should be vaccinated against whooping cough, Yeganeh said.
The vaccine doesn’t prevent 100% of infections, but those who are vaccinated and still get sick typically have milder illness, according to the CDC.
Those who have been exposed to someone with whooping cough — but are not yet sick themselves — can also get antibiotics to boost protection against illness. The CDC supports providing such post-exposure prophylaxis to all asymptomatic household contacts within 21 days of when a whooping cough patient starts coughing.
“About 80% … of people who are in the household [of a person with whooping cough] could get infected,” Yeganeh said.
A Times analysis of state data from the start of the year through the end of September shows that the greater San Francisco Bay Area has the highest per capita rate of whooping cough in the state, with 17 cases for every 100,000 residents. That’s higher than the statewide rate of 5 cases for every 100,000 residents.
The greater Southern California area has a whooping cough rate of about 4 cases for every 100,000 residents.
The Bay Area’s high rate is largely driven by high reported case rates in Marin County, where there have been 129 cases for every 100,000 residents. There were a number of cases related to transmission in schools earlier this year, but the number of cases has been declining since September.
The high reported case rate in Marin County could also be influenced by robust testing practices.
San Diego County has the second-highest case rate in the state, with 14 cases for every 100,000 residents, according to the analysis of state data.
According to local data, there have been 547 confirmed and probable whooping cough cases in San Diego County so far this year, up from 332 cases in all of 2023, officials said. Whooping cough patients have ranged in age from less than 1 month old to 85, with most cases between age 11 and 17.
“Pertussis activity continues to increase, and we are seeing an upswing in cases on track to returning to pre-pandemic numbers,” Dr. Ankita Kadakia, the interim San Diego County public health officer, said in a statement.
The rate in Los Angeles and Orange counties is about 2 whooping cough cases for every 100,000 residents, according to the analysis of state data.
Through October in Orange County, there had been 74 cases of whooping cough, the county Health Care Agency said in a statement. That’s up from the 11 cases in 2023, but still below the 185 cases seen in all of 2019.