On December 2, 2014, the Centre for Health Protection (CHP) received report of a cluster of Mycoplasma pneumoniae infections. So far, five students of a primary school were affected, they were three boys and two girls aged between six and nine. Three of them studied in the same class of primary two; the other two are siblings, one studied in primary one and the other in primary four, they both did not recall contact with the other primary two cases.

Hong Kong/CIA
Hong Kong/CIA

They presented with symptoms of respiratory tract infection, including fever, runny nose, cough and shortness of breath from November 21 to December 7. All of them required hospitalization. The clinical diagnosis of three students were pneumonia while the other two were upper respiratory tract infection. They have been in stable condition all along. Their nasopharyngeal aspirates were tested positive for Mycoplasma pneumoniae by PCR.

There had been no recent abnormal increase in respiratory tract infections among other students in the primary school. CHP has conducted field investigation and has provided health advice to the school, which was placed under medical surveillance. Investigations are ongoing.

According to the US Centers for Disease Control and Prevention (CDC), Mycoplasma pneumoniae (M. pneumoniae) is an “atypical” bacterium that causes lung infection. It is a common cause of community-acquired pneumonia (lung infections developed outside of a hospital). M. pneumoniae infections are sometimes referred to as “walking pneumonia.” Some experts estimate that between 1 and 10 out of every 50 cases of community-acquired pneumonia in the United States is caused by M. pneumoniae. However, not everyone who is exposed to M. pneumoniae develops pneumonia.

In general, M. pneumoniae infection is a mild illness that is most common in young adults and school-aged children. The most common type of illness caused by these bacteria, especially in children, is tracheobronchitis, commonly called a chest cold. This illness is often seen with other upper respiratory tract symptoms, like a sore throat. Sometimes M. pneumoniae infection can cause pneumonia, a more serious infection of the lungs, which may require treatment or care in a hospital.

Outbreaks of M. pneumoniae occur mostly in crowded environments, like schools, college dormitories, military barracks, and nursing homes, where transmission is possible through airborne droplets from close person-to-person contact. M. pneumoniae infections also frequently spread within households.