Abstract
During the period February - August 2005, an outbreak of viral hepatitis A occurred in Wiangpapao
district, Chiang Rai Province. An investigation was promptly carried out in order to determine the source
of disease transmission and provide preventive and control measures. The medical records and investigation
forms of the persons diagnosed with viral hepatitis A during the outbreak were reviewed. An
environmental survey was conducted in those areas. Proportions and attack rates were used to present
the results of the analysis.
A total of 1,308 cases of hepatitis with two deaths were detected during the outbreak. One case with
diabetes mellitus died from hyperglycemia and the other died of scrub typhus. Children aged 5-14 years
had the highest attack rate (7.5 %). The male-to-female ratio was about 1.6:1. The cases were reported
from all subdistricts in Wiangpao district. Only two cases were reported in February 2005 and a number
of cases were found in April and May 2005. Of the 438 cases examined for IgM anti-hepatitis A virus, 361
(82.4%) were positive. Contaminated ice might have been the source of transmission since a lot of cases
reported that they had consumed ice produced by one factory in the district. Samples of ice from that
factory were found it to be harbouring the causative organisms. Preventive and control measures included
the establishment of a war room for planning and supporting the activities, making improvements
in food hygiene and environmental sanitation through good cooperation with local community leaders/
schools/ owners of food, drinking water, and ice-production factories, fostering health education and a
campaign for disease prevention and control, and carrying out surveillance for cases of infection in the
areas concerned. The outbreak was curtailed after intensive preventive and control measures had been
introduced.
Continuous surveillance of food handlers and water, the conduct of health education campaigns
advocating food safety among the public, and improvements in sanitation are essential activities for preventing
or at least reducing the number of future outbreaks of food- and water-borne diseases.
