LOS ANGELES -- A ninth baby in California has died from whooping cough, and state health officials say the epidemic is on track to break a 55-year record.

Some 4,017 infections have been reported statewide this year.

Health officials say the nine deaths occurred in babies too young to be fully immunized against the illness.

Whooping cough is a highly contagious, cyclical illness that peaks in number of infections every five years.

This is a peak year, and health officials say California is on track to exceed the record 4,949 cases reported in 1955.

The last peak occurred in 2005 when California reported 3,182 cases, with 574 hospitalizations and seven deaths.

The prevalence of the disease peaks in the summer months, according to Al Lundeen, a spokesman for the state Department of Health.

Earlier in the year, state officials said twice as many cases had been reported in the first quarter compared with the same period last year.

Jonathan Fielding, the county's health director, urges parents and caretakers to get vaccinations to avoid any more deaths.

Most kids get five doses of the vaccine DTaP before kindergarten to prevent whooping cough, but those vaccines don't immunize them for life.

Health officials say most kids are once again susceptible to the disease by middle school.

A booster dose of the vaccine is recommended for people between the ages of 11 and 18, as well as for people who have contact with infants.

A typical case starts with a cough and runny nose for one to two weeks, followed by weeks or months of rapid coughing fits that sometimes end with a whooping sound.

Fever is rare.