A Maricopa County infant died of whooping cough this month, the first such death since 2009, the county Department of Public Health said.

The baby was too young to be immunized and likely contracted the illness from an adult, health officials said. They urged residents to get vaccinated if they are in close contact with children younger than 12 months old.

About 700 cases were reported in 2011 -- more than double the cases reported in 2009. Jeanene Fowler, county public-health spokeswoman, attributed the increase to more cases of whooping cough, or pertussis, and more testing being done by physicians.

The diphtheria, tetanus and acellular pertussis, or DTaP, vaccine is given to children between 2 months and 7 years old. The same vaccine for children from age 11 to adults is called Tdap. Tdap also is recommended for pregnant women in their late second or third trimester.

Vaccinations are available at primary-care doctors, pharmacies, community health centers and immunization clinics.