Compared to the first 14 weeks of 2014, in the same period in 2015, Washington has experienced a major spike in the number of pertussis cases. There were 49 cases in the corresponding period of 2014, compared to which, in 2015, there have been 319 cases.
Pertussis shows cyclical trends of increasing numbers every three to five years as there is an increase in the number of susceptible people due to waning of immunity from vaccines and previous disease incidence. Washington last experienced epidemic proportions of pertussis in 2012, when more than 5000 cases were registered.
The overall incidence of pertussis appears to be 4.7 per 100,000 population, while that for infants is massively higher at 26 per 100,000 population. Unfortunately, the disease also follows a more severe course in infants, who happen to be more susceptible to it.
It is a vaccine preventable disease and may be warded off by using the DTaP vaccine.