5 July 2010

Dear Doctor,

Rise in Mycoplasma pneumoniae in infections in Hong Kong

  I would like to inform you that the Centre for Health Protection (CHP) has detected a rise in Mycoplasma pneumoniae infections recently, possible signalling the beginning of an active phase.

  In the past, cyclical high activity of M. pneumoniae has been recorded every three to four years in Hong Kong, with the last period of high activity occurring in 2005-2006. The monthly number of positive detections by serology for M. pneumoniae ranged from three to 106 per month during 2001-2009. We observed a higher number of positive serology samples in May and June this year with monthly detections of 68 to 97 respectively. Most detections came from people aged five to 14 years.

  Infections caused by M. pneumoniae usually manifest as a respiratory illness, including pneumonia. M. pneumoniae is transmitted through contact with droplets from the nose and throat of infected people especially when they cough and sneeze. The incubation period is about three weeks (range: 1-4 weeks). Onset is gradual and common symptoms include fever, malaise, headache, chills, dry cough and sore throat. The majority of patients present with upper respiratory tract infections and patients usually recovered fully. Children and young adults are mostly affected. Transmission may result in spread in families, schools or institutions. Diagnosis is based on a rise in antibody titres between acute and convalescent area.

  About 5-10% of the patients may develop pneumonia which is usually mild and rarely requires hospitalization. It is recognised as one of the most common causes of community-acquired pneumonia in otherwise healthy patients younger than 40 years. The highest rate of infection is in individuals aged 5-20 years. Treatment with antibiotics such as erythromycin, clarithromycin or azithromycin is effective. The pneumonia often resolves without any serious complications.