Changes in the trend of shigellosis in Dhaka: family study on secondary infection, clinical manifestation and sensitivity pattern: 1980.

The incidence of shigellosis and the death rate have increased and the resistance of shigellae to antibiotics has changed in Dhaka during our experiences. In 1980, we investigated the secondary infection and case rates, infection to case ratio, duration of illness, excretion of shigellae and antibiotic sensitivity pattern in 100 families with cases of shigellosis, culturing rectal swabs obtained by home visits for a 10-day period. Standard methods were used for culture and sensitivity tests. The over-all secondary infection rate in contacts was 27.3% and the case rate 10.7%. The rates were higher for Shigella flexneri than for Sh. dysenteriae. When the index cases were nought to four years old the secondary infection and case rates were higher than when index cases were older. Contacts aged nought to four years had highest attack rates. The average duration of excretion of Sh. flexneri was 4.5 and Sh. dysenteriae 2.6 days. Illness was one day longer for Sh. dysenteriae than for Sh. flexneri. Cases of shigellosis in hospital had higher rates of fever and blood in stool than those who were not in-patients. 40% of Sh. dysenteriae and 14% of Sh. flexneri were sensitive to tetracycline, 0 to 5% to streptomycin and 100% to sulphamethoxazole, trimethoprim and gentamicin. Incidence of Sh. flexneri had increased in 1980 but that of Sh. dysenteriae remained the same as in 1973 although Sh. dysenteriae type 1 appeared to be less infective in 1980 than in 1973.