SAN DIEGO -- A 5-year-old student at Torrey Hills Elementary School in Del Mar was diagnosed with whooping cough, the San Diego County Health and Human Services Agency announced Monday.

County health officials were working with the school to notify parents of students who may have come into contact with the sick child, according to the HHSA.

The infected child was up-to-date on immunizations, according to the HHSA.

"No vaccine is 100 percent effective, but vaccinations lessen the severity of symptoms if you do become ill," said Dr. Wilma Wooten, the county's public health officer. "We encourage parents to make sure their children are vaccinated and current on all the necessary immunizations."

Whooping cough can occur at any age, but infants and young children have the highest risk of developing life-threatening complications, the most common of which is pneumonia.

Whooping cough, also called pertussis, usually starts with flu-like symptoms, such as runny nose, sneezing, fever and a mild cough. The symptoms may be mild and brief, or last up to two weeks, but are often followed by severe coughing fits that may be associated with vomiting. Whooping cough is treated with antibiotics.