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Indiana State Department of Health

Epidemiology Resource Center Home > Surveillance and Investigation > Surveillance and Investigation Division > Newsletters > Indiana Epidemiology Archived Newsletters > Epi_Newsletter_August_2007-RespiratoryIllnessIncrease Respiratory Illness Increase

Indiana epidemiology Newsletter
August 2007

Shawn Richards, BS
Respiratory Epidemiologist

Karee Buffin, MS
Vaccine Preventable Epidemiologist

The Indiana State Department of Health (ISDH) has detected an increase of respiratory illness in certain areas of Indiana. Since May, there have been reports of legionellosis, pertussis, parapertussis, Mycoplasma pneumoniae, and other community-acquired types of pneumonias.

These diseases can have significant public health impact. Legionellosis is particularly important, because it is sometimes spread by a point source within the community (such as cooling towers). Therefore, it is necessary to investigate these cases to identify the source and implement necessary control measures. Because these four diseases have certain signs and symptoms in common, appropriate diagnostic tests must be ordered to allow identification of as many cases as possible. It is also important to note that legionellosis is associated with two clinically and epidemiologically distinct illnesses: Legionnaires’ Disease, which is characterized by fever, myalgia, cough, and clinical or radiographic pneumonia; and Pontiac Fever, a milder illness without pneumonia. Legionellosis is reportable to the local health department (LHD) within 72 hours.

In reviewing the case reports, the ISDH has found that some cases reported as one of the above diseases are compatible with (and in some instances laboratory confirmed to be) one of the other three diseases. It has been noted that tests ordered for identifying these organisms according to the Communicable Disease Reporting Rule for Physicians, Hospitals, and Laboratories (410 IAC 1-2.3) do not follow recommended guidelines. Listed below are the recommended tests for each of these diseases. 

Recommended Laboratory Testing

Legionellosis:

  • Culture: isolation of any Legionella organism from respiratory secretions, lung tissue, pleural fluid, or other normally sterile fluid.

  • Urinary antigen: detection of specific Legionella pneumophila serogroup 1 antigen in urine using validated reagents. This is the fastest way to confirm the diagnosis.

  • Seroconversion: fourfold or greater rise in specific serum antibody titer to Legionella pneumophila using validated reagents. This is not recommended due to the time required to obtain both acute and convalescent sera.

Pertussis:

  • Culture: isolation of Bordetella pertussis from nasopharyngeal swabs

  • PCR using nasopharyngeal swabs

  • Seroconversion: Currently, there is no validated serologic pertussis test commercially available. Therefore, tests performed by individual laboratories may or may not be standardized and may or may not differentiate pertussis from parapertussis. The ISDH discourages clinicians from using serologic testing for pertussis for diagnostic purposes.

Parapertussis:

  • Culture: isolation of Bordetella pertussis from nasopharyngeal swabs

  • PCR using nasopharyngeal swabs

  • Seroconversion: Please refer to pertussis

Mycoplasma pneumoniae:

  • PCR (polymerase chain reaction) or direct immunofluorenscence assay (IFA) using throat swabs. This is the fastest way to confirm the diagnosis.

  • Seroconversion: fourfold or greater rise in antibody titer to specific species or serogroups of Mycoplasma pneumoniae. This is not recommended because of the time required to obtain both acute and convalescent sera