A local epidemic of hepatitis A in Piedra and Bellavista de Aserrí is being blamed on the failure to chlorinate properly the local water supply.
The Ministerio de Salud said that there were 61 cases up until Jan. 15.
The World Health Organization said that hepatitis A virus is transmitted through ingestion of contaminated food and water or through direct contact with an infectious person.
Almost everyone recovers fully from hepatitis A, but very small proportions die from fulminant hepatitis, the agency said.
The health ministry said that there were no serious cases in Aserrí. An intensive scientific investigation ruled out any other source except the local water, said the ministry.
The Caja Costarricense de Seguro Social sent workers to call on residents in the area to instruct them on how to avoid contamination. There were no cases reported in areas of Aserrí that are nearby, said the ministry. The canton is south of San José Centro.
In addition to hand washing and general attention to personal hygiene, the health ministry said that a preventative method is to put several drops of a chlorine-based household liquid for every liter of drinking water. But the water must stand for a half hour before being consumed, the ministry said.