Rich Pedroncelli, AP
An empty bottle of Tetanus, Diphthera and Pertussis, (whooping cough) vaccine is seen at Inderkum High School in Sacramento. Calif.

BOUNTIFUL — Parents of students at Viewmont High School were notified Monday of a pertussis outbreak at the school.

The Davis County Health Department reported three confirmed, one probable and two possible cases of whooping cough at the school.

A letter sent to parents indicates that "actions are being taken in order to help control the outbreak," which is characterized by two or more cases.

"The best way to prevent pertussis among infants, children, teens and adults is to get vaccinated," the letter states.

A booster dose of vaccine is recommended for individuals between 15 and 18 months old, between ages 4 and 6, and again at age 11 or 12. The vaccine is required for all Utahns prior to seventh grade, unless an official exemption is obtained for religious reasons or otherwise.

"Vaccination protects your child's health, your family's health and the health of other students and their families," the letter states.

School and health department officials are asking parents to watch for symptoms, which include runny nose, sneezing, occasional cough and possibly a low-grade fever. A cough may become more severe, resulting in long-lasting coughing spells for up to 10 weeks.

Infants and young kids are at highest risk of developing complications and even death from pertussis.

While it is a highly contagious bacterial infection, the number of pertussis cases reported throughout the state this year falls short of those reported through the same time last year, during which the state experienced more than double previous years' rates.

A total of 224 cases have been reported in 2013, while 364 cases had been reported by this time in 2012, according to the Utah Department of Health Bureau of Epidemiology. The majority of cases are in young children, but cases have been reported in all age groups in Utah.

Davis, Salt Lake and Utah counties have the highest incidences of the illness, according to the health department.

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