History and Disease Patterns


In the 1960s, researchers discovered Chlamydia pneumoniae during vaccine studies to prevent a bacterial eye infection called trachoma. Researchers first thought C. pneumoniae were a virus. Now experts know that C. pneumoniae are bacteria and are not associated with eye infections. In 1983, scientists isolated the bacteria from a respiratory culture for the first time. This development helped scientists understand how C. pneumoniae cause illness in people.

Scientists classify C. pneumoniae as “atypical” bacteria. The clinical presentation of C. pneumoniae pneumonia is different from that of “typical” pneumonia caused by bacteria such as Streptococcus pneumoniae. In addition, antibiotics usually used to treat “typical” pneumonia may not work against C. pneumoniae infections.

Disease Patterns

Since C. pneumoniae infection is likely underdiagnosed, the actual number of cases each year is unknown. The number of people who get sick from a C. pneumoniae infection does not change a lot by season.