Mycoplasma pneumoniae Outbreak in a State Institution

Indiana Epidemiology Newsletter
November 2006


Donna Allen
District 1 Field Epidemiologist

Shawn Richards, BS
Respiratory Epidemiologist


On September 22, 2006, a local health department (LHD) notified the Indiana State Department of Health (ISDH) that eight individuals housed at a State institution had developed respiratory symptoms. The institution had notified the LHD of a possible respiratory outbreak in compliance with the Communicable Disease Reporting Law for Physicians, Hospitals, and Laboratories (410 IAC 1-2.3). Symptoms were characterized primarily by cough and pneumonia.

Epidemiologic Investigation

The LHD, ISDH, and the institution initiated a collaborative investigation of the outbreak. A questionnaire was developed which documented illness and contact information. The institution’s staff members conducted interviews and completed questionnaires. Completed forms were forwarded to the ISDH Field Epidemiologist and then provided to the ISDH Respiratory Epidemiologist. The case definition was defined as any previously healthy person (staff or resident) who developed a cough and pneumonia-like symptoms on or after August 25, 2006.

Eight cases were identified. Age of the cases ranged from 30-40 years, with a mean of 39 years. The predominant symptoms included: cough (100%), pneumonia (100%), sore throat (66%), chills (57%), body aches (38%), and shortness of breath (57%) (see Table 1). The incubation period ranged from 1-4 weeks, with a median of 3 weeks (see Figure 1). Duration of symptoms varied from 5-16 days, with a mean of 10 days.

Table 1. Symptoms vs. Number of Cases
Total cases = 8





8 100


8 100

Sore Throat

3 37


4 50

Body Aches

3 37

Pulmonary Congestion

3 37

(max: 101.5°F)

5 62


1 12


4 50

*Percent based on actual number of cases

The institution staff forwarded a map of the facility to the ISDH. Cases were located on different wards of the facility. Cases were questioned about their contact with other residents, staff, or guests who were ill, and several cases responded that they had had contact with someone with a similar illness prior to their own illness onset. Those who were ill were isolated until 48 hours of antibiotic therapy were completed. Institution staff conducted surveillance for additional cases within the facility.

The institution’s health care team provided digital pictures of the chest x-rays for five cases to the ISDH. Although a specific disease agent could not be identified from analysis of the questionnaires and x-rays, tuberculosis was ruled out. Clinical specimens were submitted to the ISDH Laboratories to assist in identification of a causative agent.

Figure 1: Onset dates of illness Respiratory Outbreak, August-September 2006

Laboratory Results

The institution staff drew blood samples from the cases and submitted them to a private laboratory for serologic analysis of Legionella, Mycoplasma pneumoniae, and cold agglutinins. Sixteen nasopharyngeal swabs were submitted to the ISDH Laboratories. Three swab specimens tested positive for M. pneumoniae by reverse transcription-polymerase chain reaction (RT-PCR) testing. All swab specimens tested negative for influenza viruses and Chlamydia pneumoniae. Results obtained by the private laboratory were consistent with those from the ISDH.


This investigation confirmed that an outbreak of respiratory illness occurred among residents of a State institution during August-September 2006. The causative agent of this outbreak was Mycoplasma pneumoniae. Three nasopharyngeal swab samples were positive for this organism, and illness was compatible among all cases.

M. pneumoniae is a small bacterium that is transmitted from person to person through contact with infectious respiratory droplets. The Centers for Disease Control and Prevention (CDC) estimates approximately 2 million cases of this illness and 100,000 hospitalizations occur each year in the United States1. M. pneumoniae is one of the most common agents of community-acquired pneumonia. Sporadic infections can occur throughout the year, while outbreaks are most common during the fall, typically peaking in 4-7 year cycles3. Outbreaks can occur in closed settings or as community-wide epidemics, which may not be immediately identified2. The epidemic curve (see Figure 1) depicting the onset dates of cases indicates that this outbreak was most likely transmitted from person to person. In person-to-person outbreaks, cases become ill at different times from multiple exposures. The number of cases can gradually or sharply rise, plateau, then gradually decline. The incubation period of M. pneumoniae is 1-4 weeks,1,4 which was observed in this outbreak.

The institution, the LHD, and the ISDH collaborated on the investigation of this outbreak, completing all questionnaires, submitting digital pictures of confirmed pneumonia cases, and submitting laboratory samples. The institution initiated control measures, such as isolation and prophylaxis, to prevent secondary cases. The rapid analysis by the ISDH Laboratories was essential in identifying the causative organism. This would not have been possible without the assistance of staff members of the local hospital who provided the swabs. This outbreak had the potential to spread rapidly in a confined setting, and the prompt collaborative actions of the institution, the LHD, and the local hospital prevented that from happening.

In general, most outbreaks of respiratory illness can be prevented by strictly adhering to the following respiratory safety practices:

  1. Thoroughly wash hands with soap and water after coughing, sneezing, using facial tissue, and/or caring for someone who is ill.

  2. Cough or sneeze into your upper sleeve if possible. Discard used tissues promptly.

  3. Avoid crowded living and sleeping quarters whenever possible, especially in institutions, barracks, and ships.

  4. Frequently and thorough disinfect common areas in closed settings.

  5. Investigate contacts and sources of infection to allow for clinical treatment of those who are ill and prophylaxis of contacts and family members if appropriate.


  1. Mycoplasma pneumoniae. Centers for Disease Control and Prevention Web site: Mycoplasma

  2. Outbreak of Community-Acquired Pneumonia Caused by Mycoplasma pneumoniae–Colorado, 2000. Centers for Disease Control and Prevention. MMWR, March 30, 2001/50(12);227-230.

  3. Outbreaks of Mycoplasma pneumoniae Respiratory Infection–Ohio, Texas, and New York, 1993. Centers for Disease Control and Prevention. MMWR, December 10, 1993/42(48)931,937-939.

  4. American Academy of Pediatrics. Mycoplasma pneumoniae Infections. In: Pickering LK, ed. 2000 Red Book: Report of the Committee on Infectious Diseases. 25th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2000: 408-410.