An Outbreak of Measles in Najran Valley, December 25, 1996 - March 12, 1997.

Introduction

From Jan. 1 to March 12, 1997, an unusual increase in measles cases (35) was reported from Najran, a rural region in southwest Saudi Arabia. From 1992 through 1996 only 69 cases had been reported from the entire Najran region. An epidemiologic investigation was requested.

Methodology

We sent a new circular to all government and private health facilities requesting that they report all measles cases within 24 hours. We defined an outbreak-associated case of measles as a febrile illness with a generalized maculopapular rash of 3 days' duration and cough, coryza or conjunctivitis occurring between Dec. 25, 1996, and Mar. 12, 1997, in Najran valley. A case-control study was conducted among families with measles cases. Five and three controls were selected for case-patients < 13 years of age and > 13 years of age respectively, matched by neighborhood.

Results

The first measles case-patient was an unvaccinated 23-year-old Saudi male who had been exposed to a measles patient while visiting a neighboring region. Following the importation, three separate chains of common transmissions were identified. Community contact was identified in schools (5 cases), medical clinics (6 cases) and football matches (1 case). Most (74%) measles case-patients were over the age of coverage by universal vaccination (13) and ranged up to 41 years of age. However, females from 13 to 26 years had received a routine MMR in schools for rubella control, and only 22% of cases were in females in this group. Prior measles vaccination in the age group >13 years gave protection within the expected level (95% effectiveness) of vaccine effectiveness for measles vaccine. Near-universal vaccination in children 13 years or younger prevented computation of vaccine effectiveness in this age group.

Conclusion

Males over the age of 13 years born before the year of universal measles vaccination (1983) helped maintain a continuous chain of measles transmission in Najran. Vaccination of adolescents and young adults may be needed to prevent continuing transmission of measles in rural Saudi Arabia.