Objective: To understand the epidemiological characteristics of an outbreak of respiratory tract infection caused by human metapneumovirus (hMPV) in a primary school in Huzhou City, and to provide scientific reference for the prevention and control of the outbreak of upper respiratory tract infection caused by hMPV in the future. Methods: The investigation was carried out according to the Guidelines for Handling Influenza Like Case Outbreaks (2018 version). The throat swabs were collected to carry out COVID-19 nucleic acid test. If negative, influenza virus and other common 14 upper respiratory tract virus detection would be conducted. Results: A total of 53 cases of human metapneumovirus infection were found, the first case was found on December 15, 2020; the cases concentrated from December 21 to December 26; the last case was on December 29. It lasted 15 days and the epidemic ended. All the cases were first year students, and the incidence rate of the affected classes was 44.92% (53/118), among which the incidence rate of 101 classes was 23.08% (9/39), 102 classes was 53.85% (21/39), 103 classes was 57.50%( 23/40 ), the difference was statistically significant( χ 2=10.07, P <0.05). The age of the patients ranged from 6 to 7 years. The morbidity rate of boys was 48.00%(24/50) and that of girls was 42.65% (29/68), with no significant difference( χ 2=0.33, P >0.05). The clinical symptoms of all cases were mild, mainly cough, sore throat, runny nose, only a small number of fever. Throat swabs of 20 patients were collected, and 13 cases were positive for human metapneumovirus nucleic acid. Conclusion The symptoms caused by human metapneumovirus are relatively mild, which is not easy to attract the attention of schools and parents. Schools should carry out relevant prevention and control knowledge publicity, do a good job in the morning and afternoon inspection, and put an end to classes with diseases.

ObjectiveTo understand the epidemiological characteristics of an outbreak of respiratory tract infections caused by Mycoplasma pneumoniae （MP） in a primary school in Huzhou City， Zhejiang Province， and to provide scientific reference for future prevention and control of school outbreaks of upper respiratory tract infections caused by M. pneumoniae. MethodsAccording to the requirements for investigating respiratory infectious disease outbreaks， basic information， clinical history and epidemiological information were collected from the cases. Throat swab samples of cases for COVID-19 nucleic acid testing， influenza A and B virus antigen testing， and serum samples for detecting total antibody of mycoplasma were also collected. ResultsA total of 47 cases related to M. pneumoniae infection were identified. The first case occurred on May 4， 2022， and the cases were concentrated between May 22 and May 31， 2022. The last case occurred on June 21， marking a duration of 48 days for the outbreak. All cases were second-grade students， with an incidence rate of 35.07% （47/134） in the affected classes， with Class 206 at 53.330% （24/45）， Class 207 at 38.64% （17/44）， and Class 211 at 13.33% （6/45）. There was a statistically significant difference in the incidence rates among the classes （χ²=16.57，P<0.05）. The incidence rate was 32.39% （23/71） for boys and 38.10% （24/63） for girls， with no statistically significant difference by gender （χ²=0.48，P>0.05）. The main clinical manifestations included cough， fever， and sore throat， and some cases exhibited signs of pneumonia. Pharyngeal swabs and serum samples were collected from 27 patients. The results were negative for pharynx swab samples， and positive for total mycoplasma antibody in 12 serum samples， with a positive rate of 44.44%. ConclusionSymptoms caused by M. pneumoniae are diverse in clinical manifestations， with atypical signs and a slow progression. Early cases tend to exhibit mild symptoms. The onset of the disease is not detected in time when students are attending classes. The school morning health checks fail to promptly detect it and trigger home isolation control measures， which all contribute to the outbreak of the epidemic. Schools should conduct relevant prevention and control campaigns， improve morning and afternoon health checks， and prevent students from attending classes while sick.