Mycoplasma pneumoniae: chest infection, symptoms and UK surveillance

Mycoplasma pneumoniae is a small bacterium that infects the lining of the airways. The UKHSA data dashboard describes it as a bacterium that can cause chest infections, including pneumonia, which can affect people of all ages and is commonly reported in children and young people. UKHSA also says that tracking infections helps to monitor trends in England and identify which age groups are most affected.

The infection is sometimes referred to as walking pneumonia or atypical pneumonia because people can feel unwell but remain active. These informal terms do not appear in the UKHSA pages used here, so they are described only as common usage.

The NHS lists the symptoms of pneumonia in general, which can start suddenly or gradually over a few days, and which apply when pneumonia is caused by Mycoplasma pneumoniae. UKHSA notes the illness ranges from mild respiratory illness to severe pneumonia.

• A cough that may persist.

• Shortness of breath.

• A high temperature.

• Chest pain.

• An aching body and feeling very tired.

• Loss of appetite and, in some people, wheezing; confusion is common in older people.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have had a cough for up to 3 weeks, are coughing up yellow or green mucus, have chest pain that comes and goes or happens when breathing or coughing, or are feeling short of breath.

It advises calling 999 or going to A&E if you are struggling to breathe, have pale, blue or blotchy skin, lips or tongue, are coughing up blood, suddenly feel confused, or if you cannot wake your baby or they feel floppy.

The UKHSA pages used here do not describe how Mycoplasma pneumoniae spreads. As a general precaution for chest infections the NHS pneumonia advice applies: cover your mouth and nose with a tissue when you cough or sneeze, put used tissues in the bin quickly and wash your hands regularly with soap and water.

UKHSA says most laboratory reports are of infection in children aged 5 to 14 and adults aged 30 to 39, and it is found in children under 5 and occasionally in adults aged 65 and over. Positive tests in England have followed a cycle. The dashboard shows monthly positive tests of 649 in January 2024 and 689 in April 2024, compared with 3 in September 2026.

Most chest infections are diagnosed on symptoms and examination. UKHSA's collection describes diagnostic services, including a reference and diagnostic service and guidance on referring samples, which laboratories use to confirm the organism by testing respiratory samples. Confirming Mycoplasma pneumoniae specifically is not always needed for treatment.

In hospital, the NHS says you may be sent for a chest X-ray and blood tests to check for other conditions.

The NHS says pneumonia caused by bacteria is usually treated with antibiotics, and depending on symptoms most people get better in 2 to 4 weeks. It advises resting until you feel better, drinking plenty of fluids and taking paracetamol or ibuprofen for pain or a high temperature if you have been told you can. It says not to take cough medicine, because coughing helps the body get rid of the infection, and not to smoke.

If you are given antibiotics to take at home, keep taking them until you have finished them all, and contact your doctor if you do not feel any better after 2 to 3 days. Some people need hospital treatment: the NHS lists being over 65, having cardiovascular disease or a long-term lung condition, being a baby or young child, being very unwell, or not getting better after antibiotics.

UKHSA says the bacterium can be fatal for a small number of people and has on rare occasions been associated with severe complications such as encephalitis, inflammation of the brain. The great majority of infections are far milder.

New or worsening breathlessness, chest pain or fever after initial improvement should be reviewed by a GP.

On the NHS, chest infections are assessed by GPs, NHS 111 and urgent care services, with hospital care reserved for those who are more unwell. There is no vaccine against Mycoplasma pneumoniae. The NHS notes vaccines against other causes of pneumonia, including the pneumococcal, flu, RSV and COVID-19 vaccines for eligible groups, and that stopping smoking reduces your chance of getting pneumonia.

Private GP or paediatric services can offer faster review, but the assessment and antibiotic treatment are the same. Anyone with severe breathing difficulty needs emergency care regardless of route.