Mycoplasma Infection
("walking pneumonia", atypical pneumonia)

by Dr. Earl H. Eye, M.D.
6/16/98


What is a Mycoplasma infection?

Mycoplasma infection is respiratory illness caused by Mycoplasma pneumoniae, a microscopic organism related to bacteria but lacking a cell wall. The organism is larger than a virus but smaller than a bacterium, thus it is called an "Atypical" bacteria.

Who gets mycoplasma infection?

Anyone can get the disease, but it most often affects older children and young adults. Age is usually less than 40.

When do mycoplasma infections occur?

Mycoplasma infections occur sporadically throughout the year. Widespread community outbreaks may occur at intervals of four to eight years. Mycoplasma infection is most common in late summer and fall.

How is mycoplasma spread?

Mycoplasma is spread through contact with droplets from the nose and throat of infected people when they cough and sneeze. Transmission is thought to require prolonged close contact with an infected person. Spread in families, schools and institutions occurs slowly. The contagious period is probably fewer than 10 days and occasionally longer.

What are the symptoms of mycoplasma infection?

Typical symptoms include fever, cough, bronchitis, sore throat, headache and malaise (generalized tiredness).

A common result of mycoplasma infection is pneumonia (sometimes called "walking pneumonia" because it is usually mild and rarely requires hospitalization). Infections of the middle ear (otitis media) also can result. Less common finding are abnormalities of liver function, nausea, diarrhea, and rash.

Symptoms may persist for a few days to more than a month. New data suggest that mycoplasma may have a causal association with Rheumatoid Arthritis and chronic asthma.

How soon after exposure do symptoms appear?

Symptoms generally begin 15-25 days after exposure. The symptoms generally develop slowly, over a period of two to four days, beginning with upper respiratory symptoms, low grade fever, malaise, and coughing.

Ear pain and nasal congestion may occur. If the infection is not treated within 7-10 days of onset, a prolonged cough may occur which can last for weeks even after treatment.

How is mycoplasma infection diagnosed?

Mycoplasma infection is usually diagnosed on the basis of typical symptoms. A nonspecific blood test (cold agglutinins) is helpful in diagnosis, but is not always positive.

Serology (blood) tests are usually positive after the fifth day of illness. The use of more specific laboratory tests is often limited to special outbreak investigations. Sputum cultures are not usually done. The smear of sputum may show a predominance of monocyte type cells (initially neutrophiles) after symptoms have been present for several days which is suggestive.

Does past infection with mycoplasma make a person immune?

Immunity after mycoplasma infection does occur, but is not life-long. Second infections are known to occur, although they may be milder. The duration of immunity is unknown.

What is the treatment for mycoplasma infection?

Antibiotics such as erythromycin or tetracycline are effective treatments. However, because mycoplasma infection usually resolves on its own, antibiotic treatment of mild symptoms is not essential.

What can be done to prevent the spread of mycoplasma?

At this time, there are no vaccines for the prevention of mycoplasma infection and there are no reliably effective measures for control. As with any respiratory disease, all people should cover their face when coughing or sneezing and wash their hands frequently.

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