Outbreaks of Mycoplasma pneumoniae Respiratory Infection -- Ohio, Texas, and New York, 1993
From June through November 1993, three outbreaks of acute respiratory illness (ARI) occurred in institutional settings in Ohio, Texas, and New York. This report summarizes investigations by state and local public health officials, military personnel, and CDC, which indicate that Mycoplasma pneumoniae was the cause of these outbreaks. Ohio
From June 15 through September 5, ARI characterized by acute onset of cough and fever occurred among 47 (12%) of 403 staff members and clients of a sheltered workshop for developmentally disabled adults in Ohio (Figure_1). The median age of patients was 35 years (range: 20-60 years); seven (15%) required hospitalization, and 31 (66%) had radiographic evidence of pneumonia.
Thirty-eight persons had laboratory evidence of Mycoplasma infection: all had convalescent-phase serum antibody titers for Mycoplasma greater than or equal to 32 by complement fixation (CF), 22 (58%) had CF titers of greater than or equal to 128, and four (11%) had a fourfold rise in CF titers. M. pneumoniae was isolated from nasopharyngeal secretions of two of eight patients with available specimens. Serologic and microbiologic studies were negative for acute viral and non-Mycoplasma bacterial infections.
Although no deaths occurred among persons with laboratory-confirmed cases, one workshop participant who had not been evaluated for Mycoplasma infection died on June 30 from complications of pneumonia.
Beginning August 6, persons with ARI were excluded from work until completion of at least 3 days of antimicrobial therapy. No cases of M. pneumoniae have been identified since September 5. Texas
From August 1 through November 14, a total of 215 cases of ARI occurred among staff members at a 4500-employee tertiary-care center in southern Texas. Illnesses were characterized by abrupt onset of headache, shaking chills, and severe myalgias, followed by fever and cough. The median age of patients was 32 years (range: 19-70 years); 43 (20%) had radiographic evidence of pneumonia, and five (2%) required hospitalization.
Of 58 patients for whom paired serum specimens were available, convalescent-phase antibody titers by CF for Mycoplasma were greater than or equal to 32 for 47 (81%); fourfold rises in CF antibody titers occurred in 12 (21%). Immunoblot studies in five patients demonstrated antibody to M. pneumoniae in convalescent-phase serum specimens. Serologic and microbiologic tests were negative for acute viral and non-Mycoplasma bacterial infections.
The most recent radiographically confirmed case of pneumonia occurred on November 8. Laboratory confirmation of other ARI cases is pending. New York
On October 6, the New York State Department of Health initiated an investigation of ARI among clients and employees of an autism program in a residential developmental center in upstate New York. From August 1 through October 26, 48 cases (25%) of ARI or acute otitis media were identified among the 189 employees and clients of the program. The median age of affected persons was 33 years (range: 12-61 years). Three patients (6%) were hospitalized, 11 (23%) had radiographic evidence of pneumonia, and two (4%) had bullous myringitis.
M. pneumoniae was isolated from oropharyngeal secretions of two of five patients with available specimens. Of six patients with serum specimens available, CF convalescent-phase antibody titers were greater than or equal to 64 in two. Serologic and microbiologic tests were negative for acute viral and non-Mycoplasma bacterial infections.
From October 7 through November 10, contact between clients and employees of the autism program and the other sections of the center was restricted. The most recent patient had onset of illness on October 26. Reported by: L Smyth, S Swope, DO, L Wiser, GT Reed, DVM, Warren County Combined Health District, Lebanon; ED Peterson, RA French, MPA, FW Smith, MD, TJ Halpin, MD, State Epidemiologist, PJ Somani, MD, Director of Health, Ohio Dept of Health. M Emig, MD, RR Liu, MD, K Storms, GP Melcher, MD, MJ Dolan, MD, United States Air Force; J Schuermann, DM Simpson, MD, State Epidemiologist, Texas Dept of Health. SF Kondracki, CK Csiza, PhD, RA Duncan, MS, GS Birkhead, MD, DL Morse, MD, State Epidemiologist, New York State Dept of Health. Div of Field Epidemiology, Epidemiology Program Office; Childhood and Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.
Editorial Note: M. pneumoniae is a common cause of acute upper and lower respiratory infection in children and young adults. Infections with M. pneumoniae occur sporadically throughout the year, and outbreaks are most common during the fall, typically in 4-7-year cycles (1). However, the findings in this report suggest a potential increase in the occurrence of M. pneumoniae infections this winter.
Transmission of M. pneumoniae infections probably occurs through close contact with contaminated respiratory droplets (2). The investigations in Ohio, Texas, and New York indicate that epidemics spanning several months may occur in institutional settings where prolonged contact is common (2,3). The incubation period for this pathogen (16-32 days) (4) may contribute to protracted duration of epidemics and may limit the effectiveness of cohorting as a measure for controlling outbreaks.
The precise incidence of Mycoplasma infection is unknown because surveillance is not conducted, and laboratory confirmation is usually not obtained. However, prospective studies suggest that M. pneumoniae accounts for 15%-20% of community-acquired lower respiratory infection in adults (1,5). Approximately 20% of infections are asymptomatic; symptomatic disease is typically mild and is characterized by nonproductive cough, fever, malaise, and pharyngitis (6). Other features include myalgias (45%) and otalgia (31%); 3%-13% of patients infected with M. pneumoniae develop pneumonia (4,6). Less common complications include adult respiratory distress syndrome, pericarditis, myocarditis, hemolytic anemia, and encephalitis (1). Macrolides or tetracycline are the antimicrobials of choice for M. pneumoniae infections; however, treatment does not eradicate carriage of the organism (7). The efficacy of prophylactic antimicrobial use in outbreak settings is undetermined.
Distinguishing M. pneumoniae from other causes of acute respiratory infection is difficult because of a lack of reliable, widely available, rapid diagnostic tests. Definitive diagnosis requires isolation of Mycoplasma or a fourfold rise in CF antibody titers between acute- and convalescent-phase serum specimens, ideally obtained 2-3 weeks apart (8). Isolation of this organism can be difficult and may require up to 6 weeks (9). Although single, elevated CF titers can be useful in identifying cases in epidemiologic investigations, they are of limited usefulness for clinical diagnosis. Cold agglutinins may be present in the acute serum of 30%-60% of patients; however, this finding is nonspecific and is not useful for diagnostic purposes (8). Rapid, direct assays of respiratory secretions are being evaluated but are not widely available commercially (9).
M. pneumoniae should be considered in patients with acute respiratory illnesses, especially if associated with failure to improve when patients are treated with beta-lactam antibiotics. Persistence of the organism in respiratory secretions, despite appropriate antimicrobial therapy, may limit the usefulness of short-term cohorting during outbreaks. Prompt recognition of outbreaks in institutional settings, combined with cohorting of symptomatic patients when feasible, may avert morbidity.
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