Water supplies contaminated with sewage and toxic waste have killed at least eight people and led to around 3,500 more being treated in hospital in Karachi, a government official said on Tuesday.
Sindh province's Health Minister Shabbir Qaimkhani said his department had declared an emergency so that hospitals could give priority to fighting the gastro-enteritis outbreak in the city.
Leave for hospital staff has been cancelled and medical tents erected in the two poor neighbourhoods worst affected so that treatment can be administered quickly.
"We have enforced an emergency in government hospitals to treat the sick. We have also set up medical relief camps in the areas which have been affected to provide immediate help for the sick," Qaimkhani told Reuters.