MTPR

Missoula Whooping Cough Cases Slowing, Health Department Says

Jun 4, 2019

Whooping cough continues to be a problem in Missoula County, but local health officials think the worst may finally be behind them.

As of Tuesday, a total of 141 whooping cough – also known as pertussis – cases have been reported in Missoula County since the outbreak started back in mid-April.

Sixteen tests are pending.

Missoula City-County Health Department Director Ellen Leahy says that means the recent whooping cough outbreak isn’t over, but it has slowed down considerably.

Whooping cough is a contagious respiratory disease that can lead to severe coughing fits. Unless treated quickly, that cough can potentially last for months.

Missoula’s recent outbreak is the largest in about seven years.

"At what appears to have been the peak of the outbreak, we received 14 cases – or at least 14 cases that all had the same date of onset. That’s really high compared to three yesterday, one a few days before that. They’re coming in more slowly now," Leahy says.

Leahy attributes the slowdown to a couple of factors.

"I think part of it is the natural course of the outbreak. Also, some control measures and case-finding and trying to get those who had symptoms out of the environment where they could spread it to others."

The average age of those who contracted the disease is 17. Missoula health department nurses fanned out into local schools to find out which students possibly came in close contact with existing whooping cough patients. When a so-called "close contact" was confirmed, officials notified that person and their parent or guardian. The best medical option at that point is a prescription for antibiotics.

The Missoula Health Department temporarily hired 10 additional public health nurses this spring to chase down leads.

Summer break for most schools starts in the next week or two.

"It will dismantle that scene where there’s a lot of amplification of cases, because they are in fairly close quarters throughout the day. That in and of itself won’t end the outbreak, but it should slow things down even more."

The pertussis vaccination, while important, isn’t bulletproof. Health officials say it’s about 80 percent effective.

This graph illustrates the number of pertussis cases reported to CDC from 1922 to 2017. Following the introduction of pertussis vaccines in the 1940s when case counts frequently exceeded 100,000 cases per year, reports declined dramatically to fewer than than 10,000 by 1965. During the 1980s pertussis reports began increasing gradually, and by 2017 more than 18,000 cases were reported nationwide.
Credit Centers For Disease Control (PD)

"Even though this disease could break through an immunization, the higher the immunization rate is in the entire community or in any given setting, the less likely that that’s going to happen. Although, this one was particularly difficult because it does break through an immunization, particularly if that immunization is several years old; it does start to wane."

Adults who’ve never had a pertussis booster are urged to get one. A pertussis booster-shot for adults developed about 12 years ago is also available. It’s part of the tetanus shot. Pregnant women are urged to update their vaccinations, even if they were fully immunized before pregnancy. Newborns can’t be vaccinated until they’re 2 months old. A booster shot is available for middle school-aged children.