 In 1816 in France , a physician , J. P. A. Pasquier , described an outbreak of typhoid linked to the consumption of raw oysters . The first report of this kind in the United States was in Connecticut in 1894 . As sewage treatment programmes became more prevalent in the late 19th century , more outbreaks took place . This may have been because sewage was released through outlets into the sea providing more food for bivalves in estuaries and coastal habitats . A causal link between the bivalves and the illness was not easy to demonstrate because the illness might come on days or even weeks after the ingestion of the contaminated shellfish . One viral pathogen is the Norwalk virus . This is resistant to treatment with chlorine @-@ containing chemicals and may be present in the marine environment even when coliform bacteria have been killed by the treatment of sewage . 
