ABSTRACT
Objective To describe the epidemiological and serological features on a family associated outbreak caused by Mycoplasma pneumoniae (MP) infection occurred in Beijing in August 2007.Methods Mutual exposure of the family members was investigated and retrospective medical record was reviewed for the hospitalized patients.Serum antibodies to MP were measured and chest X-rays were taken for all the family members.Results This family consisted of 5 members,with fixed members as the boy (13 years old ),his father (43 years old) and mother (44 years old),grandmother (64 years old) and uncle (32 years old ) who was involved in taking care of the sick boy and his father.During 23 days of the event,four of all the five family members were ill.Three (boy,father and uncle) had radiographic pneumonia,whose paired sera all showed a ≥ fourfold increase in antibody titer,and two of them were confnrmed by chest X-ray on day 2 after onset of fever.The grandmother suffered from bronchitis,with positive(PA) serum antibody to MR Serum MP-IgG from the father and uncle was positive,3 days and 2 days after the onset of fever.The chances of contact between grandmother with the boy and uncle with the father were both only in the hospital wards.Only the mother remained asymptomatic,with her serum MP-IgM (-)and MP-IgG ( + )for which the blood sample was collected 37 days after close contact with the boy.The longest time of exposure to the patients was between mother and the boy but only the mother did not increase her total workload or feeling for fatigue.Conclusion Results of MP-IgG from post-infection did not completely defend against the repeated MP infection.Combined risk factors as index patients with severe cough,prolonged close contact,poorly ventilation of the environment,and family members with excessive fatigue might work as the causes of this family MP outbreak.