Pertussis cases top 2,800 in statewide outbreak

The Minnesota Department of Health has recorded 2,814 “confirmed and probable” cases of pertussis, or whooping cough, in 2024, as of Dec. 19. The majority of those cases have been reported since the beginning of October.

The vaccine for pertussis is typically administered as part of the DTaP or Tdap vaccine, both of which include the vaccine for pertussis along with those for tetanus and diphtheria. A version of a pertussis vaccine has existed since 1914, and it has been combined with vaccines for tetanus and diphtheria since 1948. In the early 1990s a change in the formula of the vaccine reduced side effects. The Mayo Clinic reports that by 2020, the number of pertussis cases that the entire U.S. typically saw was about 5,000, compared to the yearly average of 200,000 during the 20th century.

Widespread outbreak

This year has seen the most confirmed cases in Minnesota since 2012, when over 4,000 cases were recorded, according MDH data. Previous to 2012, the only years to surpass 2,500 cases were before 1948. Only 61 confirmed cases were reported in Minnesota in 2023.

The high levels of pertussis are not limited to Minnesota. Health Department data from Wisconsin reported 2,365 cases as of Dec. 20. The Centers for Disease Control and Prevention considers pertussis a National Notifiable Infectious Disease. They have recorded 33,387 confirmed cases across the U.S. this year, compared to 6,733 last year. While no single cause of this outbreak has been identified, according to the CDC, waning immunity in vaccinated populations, increases in unvaccinated populations, and genetic mutations to the virus may all be contributing factors.

Here on the North Shore

Thus far, Cook County has yet to see a confirmed pertussis case, and Lake County has had one case. St. Louis County has reported over 100 cases, and the highest number of cases have been found in Hennepin County, where the total exceeds 800. While most of the cases have been found in more populous counties, there has been a smattering of cases across rural counties. With many Minnesotans returning home from busy holiday travel seasons, cases across the state may continue to rise.

Medical Director for the Sawtooth Mountain Clinic, Dr. Paul Terrill, told WTIP that early detection and treatment is key for pertussis. He said that the virus can look like many other respiratory illnesses, but that unless it is started within the first week of symptoms, treatment will not shorten the hallmark cough that comes with pertussis, nor can it help with limiting spread.

“It can be contagious up to 3 weeks after onset, so we still want to treat with antibiotics that far out as well,” Terrill said. Pertussis is a highly contagious infection and can be particularly dangerous for young children, though people of any age can contract the virus. CDC data shows infants under one year old as the group most at risk for both being infected and for severe illness.

Because whooping cough can look so similar to other respiratory viruses, Terrill said, “The most helpful clue in diagnosing pertussis is knowing that the patient was or may have been exposed to pertussis.” He said that the incubation period for the illness can be 7-10 days, which means that symptoms may not be immediate. He added that if exposure has been confirmed, a PCR test, similar to a COVID nasal swab, can be conducted. However, the test is sent to the Mayo Clinic, and getting the results can take several days. Terrill said that because of the delay, treatment can be started before results are returned, in an effort to both shorten illness, and to prevent further spread.

The MDH has a full list of symptoms that could indicate pertussis. They advise that while the “whoop” sound between coughs is a symptom, not everyone with pertussis will experience the distinctive whoop, especially if they have previously received a vaccine.

For Cook County residents who may have fallen ill over the holidays, Terrill shared some advise, “If you have a respiratory infection of any kind that includes a cough that has been going on for less than 3 weeks, wearing a well-fitting surgical mask when in public will help reduce the spread. If you have a cough and know you have been exposed to pertussis, please call us at SMC and let us know that history. It will help us take the best care of you and also help us minimize the risk of spreading it to others.”

Kirsten Wisniewski December 30, 2024