Mycoplasma pneumoniae is a type of "atypical" bacteria that commonly causes mild infections of the respiratory system. In fact, pneumonia caused by M. pneumoniae is sometimes referred to as "walking pneumonia" since symptoms tend to be milder than pneumonia caused by other germs. The most common type of illness caused by these bacteria, especially in children, is tracheobronchitis, commonly called a chest cold. Symptoms often include being tired and having a sore throat, fever, and cough. Sometimes M. pneumoniae can cause pneumonia, a more serious lung infection, which may require care in a hospital.

How Do You Say That?

Find pronunciation guides below for common words associated with Mycoplasma pneumoniae.

• Mycoplasma — MY-ko-plaz-ma
• Pneumonia — noo-MOAN-yah
• Pneumoniae — noo-MOAN-e-a
• Tracheobronchitis — TRAY-key-o-brahn-KITE-uss

• Mycoplasma pneumoniae is a small bacterium that infects the lungs and other parts of the respiratory tract. People can spread these bacteria to others by coughing or sneezing.
• Pneumonia caused by M. pneumoniae is considered an atypical bacterial pneumonia because:
  • It tends to cause milder illness but symptoms tend to last longer
  • It can appear differently on an x-ray
  • The antibiotics commonly used in the past to treat bacterial pneumonia did not work against it
• Symptoms of illness caused by M. pneumoniae usually start gradually. It can take someone between 1 to 4 weeks to get sick after they are exposed to the bacteria.
• Most M. pneumoniae infections are mild and get better on their own without treatment, but serious complications can occur.
• An estimated 2 million cases of M. pneumoniae infections occur each year in the United States. The true number is unknown and likely underestimated.
• M. pneumoniae is the second most common cause of pneumonia-related hospitalization in adults with community-acquired pneumonia (lung infections developed outside of a hospital).
• M. pneumoniae may cause between 1 and 10 in every 50 cases of community-acquired pneumonia in the United States.

Causes

Mycoplasma pneumoniae is a type of bacteria that causes illness by damaging the lining of the respiratory system (throat, lungs, windpipe).

How It Spreads

M. pneumoniae spread from person to person. People without symptoms may carry the bacteria in their nose or throat at one time or another. People spread M. pnuemoniae by coughing or sneezing, which creates small respiratory droplets in the air that contain the bacteria. Other people then breathe in the bacteria.

Most people who spend a short amount of time with someone who is sick with M. pneumoniae do not become ill. However, it is common for the bacteria to spread between people who live together. M. pneumoniae infections usually have long incubation periods (the time between breathing in the bacteria and developing symptoms). The incubation period is usually between 1 to 4 weeks.

M. pneumoniae outbreaks occur mostly in crowded settings like schools, college residence halls, military barracks, nursing homes, and hospitals. During school-based outbreaks, if people in the community get sick it is usually family members of ill school children.

The most common type of illness, especially in children, is tracheobronchitis, commonly known as a chest cold. Common symptoms of a chest cold include:

• Sore throat
• Fatigue (being tired)
• Fever
• Slowly worsening cough that can last for weeks or months
• Headache

Experts have estimated that up to 1 in 10 people who get ill from M. pneumoniae get pneumonia. Common symptoms of pneumonia include:

• Cough that may produce mucus
• Fever and chills
• Shortness of breath
• Chest pain
• Fatigue

Children younger than 5 years old often do not run a fever when they have an illness caused by M. pneumoniae. Instead they may have signs that appear more like a cold than pneumonia. They sometimes wheeze, vomit, or have diarrhea.

Mycoplasma pneumoniae infections are most common in young adults and school-aged children, but can affect anyone. People at increased risk include those who live or work in crowded settings, such as:

• Schools
• College residence halls
• Military barracks
• Nursing homes
• Hospitals

People at increased risk for serious infections include people:

• Recovering from a respiratory illness
• With a weakened immune system

Treatment

Most people will recover from an illness caused by Mycoplasma pneumoniae without medicine. However, if someone develops pneumonia (lung infection) caused by M. pneumoniae, doctors usually prescribe antibiotics as treatment. Antibiotics can help patients recover from the illness faster if started early on.

There are several types of antibiotics available to treat pneumonia caused by M. pneumoniae. If a doctor diagnoses you or your child with an M. pneumoniae illness, your doctor will explain how to treat it.

Some M. pneumoniae are resistant to some antibiotics used for treatment.

Complications

While M. pneumoniae usually causes mild disease, severe complications can occur, resulting in needing care in a hospital. M. pneumoniae infections can cause or worsen the following complications:

• Serious pneumonia
• Asthma attacks or new asthma symptoms
• Encephalitis (swelling of the brain)
• Hemolytic anemia (too few red blood cells, which means fewer cells to deliver oxygen in the body)
• Renal dysfunction (kidney problems)
• Skin disorders (Stevens-Johnson syndrome, erythema multiforme, toxic epidermal necrolysis)

• Cover your mouth and nose with a tissue when you cough or sneeze.
• Put your used tissue in a waste basket.
• If you don’t have a tissue, cough or sneeze into your upper sleeve or elbow, not your hands.
• Wash your hands often with soap and water for at least 20 seconds.
• If soap and water are not available, use an alcohol-based hand rub.

There is no vaccine to prevent M. pneumoniae infections.

Previous Infections

Life-long immunity (defense to or protection from future infections) to M. pneumoniae likely does not occur. If you get sick from M. pneumoniae, you may get sick from it again in the future.

Antibiotics

Antibiotics can help treat patients with pneumonia caused by M. pneumoniae. Doctors generally do not prescribe antibiotics to help prevent someone else from getting sick (for example, a close contact of an infected person).

History

As early as the 1930’s, scientists were reporting pneumonias that were “atypical” compared to characteristics seen in “typical” pneumonias. Patients with atypical pneumonia tended to be not as sick, have symptoms for longer, and not respond to some antibiotics used for treating “typical” pneumonia. In 1944, scientists discovered the agent that cause “atypical” pneumonia, later named as Mycoplasma pneumoniae. They first thought it was a virus or fungus so they chose the name “mycoplasma,” which is Greek for “fungus-formed.” Eventually, scientists learned that it is a bacterium with many unique characteristics. For example, it does not have a rigid cell wall, which affects the types of antibiotics that work well against it. It is also the smallest organism capable of living and reproducing on its own. Smaller germs, like viruses, have to live and reproduce inside cells.

Disease Patterns

M. pneumoniae infections are common in the United States. The number of infections varies over time, with peaks of disease every 3 to 7 years. An estimated 2 million cases of M. pneumoniae infections occur each year in the United States. However, many infections are not diagnosed, so the actual number is likely higher. This illness can happen any time during the year but may be more common in summer and early fall.