At least 364 pertussis infections were reported to health authorities last week, according to figures published Thursday by the Centers for Disease Control and Prevention, marking the worst Thanksgiving week for whooping cough in recent decades.

This tops the previous Thanksgiving record of 228 cases of pertussis which were reported for the week ending Nov. 27, 2010. That year there were 27,550 cases reported by the end of 2010, below the 28,167 already tallied so far this year. 

Thanksgiving usually sees a slowdown in cases reported across most diseases, because of delays in testing and reporting around the holiday as well as changes in people going to the doctor.

But this year’s whooping cough wave is continuing to accelerate in several states this week, including in Ohio, which reported 84 cases. That is the most of any state, and more than the 67 pertussis cases that Ohio reported in the week before.

“Pertussis can be cyclical. After seeing lower numbers of reported cases in the past few years — during and after the COVID-19 pandemic — nationally, pertussis is now returning to pre-pandemic trends. Ohio is no different,” a spokesperson for Ohio’s health department said in a statement.

The Ohio spokesperson said this year’s increase remained “consistent with some years prior to the COVID-19 pandemic,” and has yet to top the total number of cases reported in 2013.

While total cases nationwide remain lower than some previous records, the pace of weekly reported cases reached 577 ahead of Thanksgiving — more than 10 times the same time last year, and the worst in at least a decade.

Health officials have cited a variety of factors for this year’s wave of whooping cough cases, including gaps in immunity from vaccination or prior infection and the switch to safer but less effective vaccines in the 1990s.

“We have to acknowledge that our vaccination rates, in Montgomery County for school-age children, are low. They’ve decreased since the pandemic, and they’re lower than the state of Ohio, and lower than the United States as well,” said Dr. Becky Thomas, medical director of the health department for Ohio’s Montgomery County.

Within Ohio, Montgomery County makes up the largest share of cases reported in recent months, despite not having the most people in the state. 

Around 63% of their cases have been in schoolchildren and 12% are in daycares, Thomas said. The department often finds out about outbreaks first from school nurses, warning of large numbers of kids calling out sick with whooping cough.

Thomas said doctors have been seeing high pertussis case counts for months, larger than the wave they saw last year.

“We had an increase in cases last fall, but nothing compared to this fall. And when we first started noticing a really significant increase was about the time that kids went back to school, so about the middle of August,” said Thomas.

Thomas said that the vast majority of reported cases in the county have said they were vaccinated for pertussis, though it is unclear if everyone was up-to-date on the shots. A third of cases have been in teens, who are recommended to have gotten a booster dose by age 12.

“We have specific data on vaccination records for entering seventh graders that shows those vaccination rates for that tetanus, whooping cough vaccine that they should have entering school are decreased,” said Thomas.

This year’s whooping cough surge also comes as health departments are bracing for the return of an expected wave of COVID-19 and flu infections this winter.

“Whooping cough isn’t the only respiratory illness that we’re concerned about. So we’re encouraging people to stay home when they’re sick, practice good hand hygiene, get their health care provider if they need to if they’re symptoms are worsening or severe, and of course get vaccinated,” said Jennifer Wentzel, the county health department’s commissioner.