Officials with the Kennewick School District confirmed Thursday two cases of whooping cough at Cottonwood Elementary and Desert Hills Middle schools.
A third student was being examined for also possibly having the infectious disease.
Whooping cough, or pertussis, is known for the distinctive cough it causes. The disease is preventable through vaccination.
The latest cases brought the tally for 2012 to five cases in Benton and Franklin counties. There were 11 cases last year.
"Obviously, we're going to be way over our 2011 levels," said Amy Person, health officer for the Benton Franklin Health District.
Letters will be sent home with all Kennewick students today informing parents of the situation and how the district is cooperating with health authorities.
District spokeswoman Lorraine Cooper said one of the confirmed cases involves an elementary student and the other is a middle school student. Person said the students are being treated and are out of school but are not hospitalized.
Whooping cough is a bacterial infection that causes respiratory problems and is spread by coughing and sneezing, according to information from the Washington Department of Health. The disease has mild symptoms at first, but soon develops into severe coughing fits that can last for weeks. Antibiotics are used to treat the disease.
Children and adults can suffer from pneumonia, trouble sleeping, incontinence and broken ribs from the illness. Infants particularly are at risk and can die as a result of infection.
Person said people should seek medical attention if they have a cough that is persisting. Practicing good hygiene, such as regular handwashing, also prevents the disease from spreading.
Cooper said that students who are vaccinated against the disease won't get infected. However, she said a child's immunity from the initial set of childhood vaccinations begins to wear off around the age of 10. A booster shot that covers whooping cough, along with tetanus and diptheria, can extend a child's immunity.
While most students are vaccinated, not all are. Kennewick, along with other public school districts, allows parents and guardians to exempt their children from vaccinations on health and religious grounds. The number of children in the district who are not vaccinated was not immediately available Thursday.
Last year, 29 cases of whooping cough were reported in Grant County. There were 57 cases investigated by the health district during the 16-month outbreak, which included one infant death.
In the previous five years, Grant County reported one to four cases a year. State records show two infants died from whooping cough in Yakima and Snohomish counties in 2011.