The California Department of Public Health announced that there have been 4,017 confirmed, probable and suspect cases of whooping cough (pertussis) reported in the state so far this year, up to September 14 – a state rate of 10.3 cases per 100,000 people. The number of weekly reported cases has dropped slightly recently, with 183 new cases this week and 234 cases the week before.

The last time so many cases were reported was in 1955, with 4,949 cases. The current incidence of whopping cough is the highest since 1962, when it reached 10.9 cases per 100,000 people. The previous peak in total reported cases was in 2005 (3,182 cases).

Of the reported cases, health authorities say 65% are confirmed, 20% are probable and 15% are suspect.

Authorities say 11.2% of infected patients have been hospitalized. 57% of those hospitalized were infants (vey young babies).

Of the 9 deaths reported so far:

8 were Hispanic infants

8 were infants aged less than two months at the time of disease onset

None of the 8 infants less than two months old had received any doses of pertussis-containing vaccine

1 was an ex-28 week premature baby who was 2 months old at the onset of the disease who had received the first dose of DTaP 15 days before becoming ill.

Health authorities inform that of the babies who have caught whooping cough, the majority are infants aged three months or less.

The incidence of whooping cough (pertussis) is highest among babies aged up to six months – 184 cases per 100,000; in children aged 7-9 years – 33 cases per 100,000; and adolescents aged 10-18 – 24 cases per 100,000.

Most adolescent cases are aged 10 or 11 years.