Overview of Waterborne Pathogens - Waterborne Pathogens: Detection Methods and Applications - page 16

different diseases and symptoms. Enteroviruses have been found in both raw
water sources and treated water.
2.1.4. Hepatitis viruses A and E
Hepatitis A and E belong to different groups. Hepatitis A is similar in size
and structure to enteroviruses, though it has its own genus (Hepatovirus),
of which it is the sole member. The infectious dose for hepatitis A virus is
estimated to be about 10-100 infectious particles 11 and it is able to persist
for a very long time in a water environment. The infection proceeds via the
epithelial cells, lining the intestine, into the bloodstream, eventually infect-
ing the liver. The incubation period is normally around 48 days. 8 In around
90% of cases there is no liver damage, especially in very young children, and
lifelong immunity is incurred. However, the severity of the illness increases
with age. 8
The size and structure of hepatitis E is not so different from hepatitis
A. It also consists of single-stranded RNA in a nonenveloped icosahedral
capsid, with a diameter of 27-34 nm. The symptoms of infection are also
fairly similar to hepatitis A, though often symptoms are more severe and
those infected are slightly older. It also results in a 25% mortality rate among
infected pregnant women. The incubation period is 60 days. Several large
waterborne outbreaks, infecting tens of thousands, were reported in the
1980s and 1990s in India and China. 9
2.1.5. Norovirus
NoV is one of the four genera of caliciviruses. Two of these caliciviruses
are infective to humans, with sapoviruses being the other. NoV consists of
single-stranded RNA in a nonenveloped icosahedral capsid. The size of this
virus is around 35-40 nm in diameter. Unlike the other caliciviruses, NoV
does not usually display a cup-like structure in the surface morphology.
This virus causes acute gastroenteritis in all age groups, and it can be
particularly serious for the elderly or immunocompromised. The incuba-
tion period is normally around 48h with the self-limiting illness lasting
24-48 h. In around 40% of cases, the main symptom is diarrhea, whereas
other patients exhibit no diarrhea but suffer vomiting instead. The infection
is sometimes referred to as the winter vomiting sickness. Infection with
NoV confers a short-lived immunity.
The infectious dose for NoV is estimated to be about 10-100 infectious
particles, 12 and therefore, although the viral load in water samples may
be low, it may still be a source of infection and illness. Additionally, NoV