Five school-age children in Douglas County have been diagnosed with cases of pertussis, or whooping cough.

The cases don’t appear connected, said Sheryl Tirol Goodwin, a Lawrence-Douglas County Health Department spokeswoman.

Pertussis is a highly contagious respiratory infection that can result in pneumonia or brain swelling if not treated. Symptoms resemble the common cold, but the coughs worsen in frequency and severity.

The county has had 16 cases this year, but the recent ones are the first since spring, Tirol Goodwin said. In 2005, the county had 43 probable or confirmed cases.

The health department also announced Wednesday an additional case of giardiasis, which makes six for the county. The infected child attends Princeton Children’s Center and has also tested positive for cryptosporidiosis.

None of the cases involve swimming pools, and health officials said they believe they have the bacterial diseases, which are spread by fecal-oral contact, contained, Tirol Goodwin said.