More than 3,500 cases of pertussis, or whooping cough, cases have been reported in Texas so far this year, already reaching a 11-year high even though two more highly infectious months are left in the year, according to the Texas Department of State Health Services.

The uptick in whooping cough, which is especially contagious in children, has coincided with a decline in vaccination rates for the illness, according to disease experts who urge the best way to control the spread is to get vaccinated. They also say whooping cough tends to spike every few years and that there isn’t a way to completely wipe out the disease.

“We practitioners and public health professionals are concerned because we are seeing a year-after-year trend of a significant increase in cases when this is preventable,” said Hector Ocaranza, a pediatrician and member of the Texas Medical Association’s Council on Science and Health Promotion. “Especially a disease that can have such a severe effect on infants, older people, and those who have chronic conditions.”

The Texas Department of State Health Services reported more than 3,500 cases of whooping cough through October, quadruple the number of cases during the same period last year, which saw a total of 1,907 cases, according to provisional data. The total so far is also 10 times the number of cases for all of 2023. This is the second consecutive year the state’s health agency has had to issue a health alert.