Pertussis (Whooping Cough) Outbreaks and Cases on the Rise

I do not recall a time that a college football game was cancelled due to a pertussis (whooping cough) outbreak, but that was just recently the case when an outbreak occurred among members of the Portland State football team just before they were scheduled to play South Dakota. That game was cancelled, and for a while, it was uncertain whether Portland State would have to cancel its scheduled match-up with Boise State, as well, but that game was able to go forward on September 21 – this past weekend.

Meanwhile, here in Idaho, the Bonner County Daily Bee Pertussis outbreak continues in region | Bonner County Daily Bee is reporting on a pertussis outbreak in the Panhandle – northern Idaho. According to reports from the Panhandle Health District as reported in the article, “Since April, the number of reported pertussis cases in North Idaho has grown from a few dozen to 166 as of mid-September, and that number is continuing to increase.” Keep in mind, the number of actual cases is almost certain to be far more than the number of cases reported, as not everyone with pertussis seeks or requires medical attention.

For comparison, Panhandle Health District only had nine total cases of pertussis over the past three years — five in 2023, three in 2022, and one in 2021.

The CDC also reports that cases of pertussis in the U.S. are on the rise this year. So far this year, cases are about three-times that reported in 2023.

One reason I was surprised about the outbreak among members of the Portland State football team, besides the fact that I had never heard of a college game being cancelled for this reason, is that although people of all ages can get pertussis, it is largely a disease that affects children and adolescents. Babies younger than one year old are at greatest risk of getting pertussis and developing severe complications. Of infants who develop whooping cough, roughly one-third need to be treated in the hospital. Whooping cough is particularly dangerous for these babies and infants because their airways are smaller and less well developed and generally, they have no prior existing immunity unless their mothers were vaccinated against pertussis during the pregnancy.

Pertussis is highly infectious. It is caused by bacteria called Bordetella pertussis. It is transmitted through respiratory droplets, predominantly, by coughing, sneezing, or even normal breathing when in close contact with others. This bacterium attaches to cells lining the upper airways that have hair-like extensions that act to help mobilize secretions and debris that we breath in from the air – these hair-like structures are called cilia (pronounced sil-E-ah). However, this bacterium releases a toxin when it infects cells and this toxin damages the cilia and often causes the airways to swell. This can cause choking, paroxysms of coughing sometimes severe enough and prolonged enough to cause vomiting, and in these young children, it can lead to a characteristic sign that gives the disease its name – whooping. Often, after one to two weeks of first presenting as a cold-like illness, the coughing phase begins and these infants may have a series of coughing fits followed by what seems like a prolonged effort to get a deep breath in that is accompanied by this “whoop” sound and the infant’s chest may cave in a bit. Even more worrisome is that some babies don’t develop these signs, but rather may have periods in which they stop breathing (apneic spells). While most of these children will recover, tragically, about 20 babies die per year from this infection.

While older children and adults don’t generally develop compromised breathing, the coughing can be quite bothersome and, in some cases, pneumonia can develop. Pertussis can be treated with antibiotics. Often times, a physician will make the diagnosis empirically, i.e., simply based upon typical signs and symptoms being present, especially when an increase in cases have been reported in the community. However, pertussis can be confused with other illnesses like RSV (respiratory syncytial virus), COVID-19, and influenza, so when in doubt, testing for this bacterium can be done with a PCR test from a nasal swab, like most persons experienced early on in the COVID-19 pandemic when testing for the SARS-CoV-2 virus. Given how contagious this infection is, the decision may be made to treat others in the family with antibiotics who are not yet showing signs or symptoms of the disease prophylactically when someone in the household is infected.

We begin DTaP vaccinations for babies at two months old and use this vaccine for children up to age 7. The “D” stands for diphtheria, another bacterial (Corynebacterium diphtheriae) infection that results from the toxin produced by this bacterium that can cause a grayish membrane to form in the back of the throat that can interfere with swallowing and breathing and cause an emergency. The “T” stands for tetanus toxoid, the stimulus for the immune system to protect the body from the life-threating toxin produced by the bacterium (Clostridium tetani) that causes the disease tetanus or more colloquially known as “lockjaw.” Finally, the “aP” stands for acellular pertussis, and this component of the vaccine consists of several protein antigens (antigens are recognized by the body as not part of the body and stimulate an immune reaction and the production of antibodies and the development of cellular immunity) from the bacterium and is referred to “acellular” to distinguish it from earlier vaccines that contained the entire cell of the bacterium. The acellular form of the vaccine is used in most developed countries because it results in far fewer side effects.

We then shift to the Tdap vaccine once children are around 11 or 12 years of age, and continue with this vaccine every ten years to boost the immune response, which does wane over time. The lower-case letters for “D” and “P” reflect that the dosage (amount of the vaccine component) has been reduced. This is also the formulation we often recommend for pregnant women during the 27^th – 36^th weeks of pregnancy in order for the mother to form antibodies that are then transferred to the infant and help protect that newborn until we can begin the baby’s vaccination series at 2 months of age. Many physicians will also recommend that the father and grandparents who are going to be in close contact with the baby get this vaccine to reduce the likelihood that they get infected and then pass the infection on to the vulnerable infant.