Many human calicivirus outbreaks have been epidemiologically linked to contaminated
drinking-water supplies. Within a water safety plan, control measures to reduce
potential risk from human caliciviruses should focus on prevention of source water
contamination by human waste, followed by adequate treatment and disinfection. The
effectiveness of treatment processes used to remove human caliciviruses will require
validation. Drinking-water supplies should also be protected from contamination during
distribution. Owing to the higher resistance of the viruses to disinfection, E. coli
(or, alternatively, thermotolerant coliforms) is not a reliable indicator of the presence/
absence of human caliciviruses in drinking-water supplies.