Pertussis (whooping cough) at epidemic levels

expired

In 2010, pertussis was at a record high with 233 cases reported in Washtenaw County residents. As of April 28, twenty-one cases cases have been reported for 2011 which is still above normal levels.

The total number of cases for 2009 was 84, which had been the highest number seen in years.  

Why is there such a big increase in pertussis cases?

Some likely reasons include:

  • Decreasing immunity in teens and adults. Many have not yet gotten their Tdap vaccine booster, and more than half of this year’s cases have been in teenagers and adults.
  • Unvaccinated children. Parents who opt out of vaccinating their children create pockets of vulnerability in the community.   
  • Change in pertussis testing.  A newer test, called a PCR, has become the dominant method of testing and most likely we are detecting more cases than we would have in the past.

Graph of pertussis cases by month: 2009 vs. 2010 (pdf)

Profile of Washtenaw 2010 pertussis cases:

Age group Number of cases (%) Hospitalized

 < 1 year

11 (5%)

 1 - 4 years

24 (10%) 

 0

 5 - 9 years

56 (24%) 

 0

10 - 19 years 

78 (34%) 

 0

 20 - 64 years

61 (26%) 

 3

 65 and older

 2 (1%)

0

Area

Number of cases (%)

 Ann Arbor

 120 (52%)

 Saline/Milan

 41 (18%)

 Ypsilanti

 46 (20%)

 Manchester/Dexter
Chelsea/Whitmore Lake

 25 (10%)

Vaccination status:

Pertussis vaccination is routinely given at 2, 4, and 6 months of age and then at 1 year and 4 years, so that children have 5 doses of vaccine by the time they enter kindergarten. A booster dose of Tdap is now given to teenagers and adults, since immunity wanes over time.  In Michigan, parents are allowed to opt out of vaccinating their children. 

In 2009, of the Washtenaw pertussis cases aged 0 to 4 year olds, 50% had no pertussis vaccine. Similarly, 53% of 5 to 9 year olds were unvaccinated against pertussis.  In the 10 to 17 year-old group, 69% had received 5 doses of pertussis vaccine but only one of the children had received the adolescent booster of Tdap.  In some families, older children were vaccinated against pertussis and the younger ones were not. In almost all of these situations, the vaccinated children did not become symptomatic. 

What is pertussis?

Pertussis is a very contagious disease of the respiratory tract caused by bacteria called Bordatella pertussis. Pertussis is also known as “whooping cough” due to the “whoop” sound made when the infected person tries to breathe after hard coughing and choking spells. Children younger than 6 months of age may not have the strength to have a “whoop”. Also, many adults and teenagers with pertussis do not have a classic “whoop”. 

Pertussis symptoms include:

  • low grade fever
  • runny nose
  • cough which becomes more severe after 1-2 weeks. Cough often lasts for more than a month.

During coughing attacks, the lips and nails may turn blue for lack of air. Vomiting can occur with severe episodes. In between coughing episodes people may feel and appear fairly healthy. Some report that coughing is worse at night. In children less than 1 year old, complications include pneumonia, convulsions, and, in rare cases, brain damage. The majority of deaths from pertussis occur in infants younger than 2 months of age.

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