OBJECTIVETo identify the cause of an outbreak of foot pain syndrome among students from a senior high school in Foshan.

METHODSWe defined a suspect case as onset of foot pain/numbness with unknown reason among students and teachers in a school of Foshan city, from February 10 to March 16, 2014. A suspect case was noticed as having both food pain and numbness. All the cases were searched through reviewing medical records in the nearby hospitals and school's clinic, also the records of absenteeism in school. Clinical information was collected from all the students, using a standardized questionnaire. Daily temperature was collected from all the students, between January 1 and March 31, 2014. A 1 : 2 individual matched case-control study was conducted to identify related risk factors on this epidemic. We interviewed all the cases and controls on their diet, physical activities and measures used for warming.

RESULTSA total of 407 case-students were identified, with an attack rate (AR) as 26.5%. The AR was 37.3% in girls, compared to 12.9% in boys. The difference was statistically significant (χ² = 115.1, P < 0.01). Boarding students had a higher AR (31.8%) than the commuting students (16.2%). The difference was statistically significant (χ² = 43.2, P < 0.01). In girls, boarding students had higher AR (46.1%) than those commuting students (18.5%). The difference was statistically significant (χ² = 61.4, P < 0.01). No statistically significant difference was found between boarding or commuting students in boys. Outdoor temperature was coming down from 23 °C on February 6 to 6 °C on February 13, but gradually rose to 23 °C on February 28. There was a positive relationship (r = 0.65, P = 0.002) noticed between daily maximum temperature and the number of cases during February 13-28. Results from this case-control study showed that factors as lacking physical activities (OR = 2.8, 95% CI: 1.5-5.6), feeling cold in bed (OR = 3.0, 95% CI: 1.3-7.0) and having experienced similar symptoms (OR = 3.4, 95% CI: 1.1-11.0) could increase the risk of this disease.

CONCLUSIONThis outbreak was possibly caused by the abrupt fluctuation of temperature within a short period.

Case-Control Studies ; China ; epidemiology ; Disease Outbreaks ; Female ; Foot Diseases ; epidemiology ; Humans ; Male ; Pain ; epidemiology ; Residence Characteristics ; statistics & numerical data ; Risk Factors ; Schools ; Students ; statistics & numerical data ; Surveys and Questionnaires ; Syndrome ; Temperature ; Time Factors ; Transportation ; statistics & numerical data