The hospital earlier said 22 kidney patients had been infected with hepatitis C between April and June.
Eight died with four of the deaths linked to the viral infection and another still under investigation.
The cause of the outbreak has left the medical community stumped.
Hepatitis C is usually spread through unsafe injection practices, poor sterilisation of medical equipment and unscreened blood transfusions, according to the WHO.
The use of multi-dose vials of medicine has been cited as a possible cause of the outbreak in Singapore, expect that new needles and syringes are used for each dosage.
The apparent delay in alerting the public has also caused indignation in Singapore, which prides itself on a modern healthcare system that attracts patients from around the world.
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