On Sunday 5/4/2009, the Preventive Medicine Department of the General Health Directorate of the Eastern Region reported an unusual increase in the number of Mumps cases reported from three international schools in the region. The total number of cases reached 59 cases since the beginning of 2009. The Field Epidemiology Training Program (FETP) was assigned to verify and investigate this outbreak and recommend control measures.
Methodology
FETP team visited the Regional Health Directorate and Preventive Medicine Department of the Eastern Region and reviewed the available information to establish the existence of an outbreak. Then the team decided to visit the three international schools to collect some additional information about the cases. On Tuesday 7/4/2009 the team conducted a case-control study. A case was defined as any person attached to one of the three international schools who had developed an illness with acute onset of unilateral or bilateral tender, self-limited swelling of the parotid or other salivary gland(s), lasting at least two days, and associated with fever, with or without serological confirmation during the period from 1/12/2008 to 4/5/2009. The controls were class mates of the cases that had not developed any symptoms during the same period. A questionnaire was prepared and filled by face to face interview and by reviewing records.
Results
During the study period a total of 153 persons were interviewed, 59 cases and 94 controls. Out of the cases 53 (89.8%) were from one school (International Indian School in Khobar), the rest six cases were from the other two schools (four from Almuatasim International School in Jubail and two from New World International School in Khobar). Most of the cases 52 (88.1%) were Indians. Males were 53 (89.8%). The mean age was 13.8 years (± 5.3) (range 5-39 years). Symptoms appeared on the first case on 26/12/2008. She was a Srilankan teacher from Almuatasim International School in Jubail who had just arrived two weeks earlier from vacation in her country. The propagation of the infection between schools came by contact between some of students from two of the schools in an evening course in Khobar. All cases developed parotid swelling, unilateral in 22 (37.3%) and bilateral in 37 cases (62.7%), 48 cases (81.4%) developed fever, and 12 of the male cases (20.3%) complained of scrotal pain. Out of all cases 38 (64.4%) had received Mumps vaccination. Among 44 cases (74.6%) who did blood serological test, 26 (59.1%) had a positive result of Mumps IgM. Vaccination status of both cases and controls was not clear and not documented in all the 3 schools and its presence was not mandatory in the school records or registration.
Conclusion
The Srilankan teacher from Almuatasim International School in Jubail was probably the index case in this outbreak. Most of the cases were between 13-16 years of age which can be explained by fading of the effect of the last MMR vaccination which is usually given at school entry. Delayed notification by the International Indian School in Khobar led to this high number of cases especially in this school, since preventive measures were also delayed. Isolation of cases at home and implementation of a 1 dose of MMR vaccination to all ofthe students in the 3 schools was recommended for the control of this outbreak.