Epidemiologic pattern of diarrhoea caused by non-agglutinating vibrios (NAG) and EF-6 organisms in Dacca

Non-agglutinating vibrios (NAG) and a new organism (EF-6) caused a severe diarrhoea epidemic in Dacca in 1976 and 1977. The common NAGs detected were groups II, V and VII which were present all the year round with peaks in the spring and postmonsoon seasons, while EF-6 attained its peak in March. NAG and EF-6 diarrhoeas occurred all over the city. The NAGs and EF-6 infected males twice as often as females and EF-6 more often affected the age group 0-4. The secondary attack rates in contacts of NAGs ranged from 10% to 25%; there were none in the EF-6 affected families. Open sources of water were often contaminated with NAGs and occasionally with EF-6. About half of the isolates from contacts and water sources were of groups other than the index case. Water was thought to be the vehicle of transmission.