Drinking-water-viruses

DRINKING WATER -- VIRUSES

INDEX TO SOME VIRUSES IN SLUDGE BIOSOLIDS AND RECLAIMED WATER not included in AWWA M48
Viruses replicate in heterothropic parts of cells--
25 million young girls and women infected with cancer causing papillomas virus, which requires
intermediate to high level liquid chemical germicide to inactivate in laboratory

Drinking water Bacteria and parasites

AWWA
EFFECTIVENESS OF WATER TREATMENT PROCESSES _ ON VIRUSES

A denoviruses
Chlorine disinfection studies of human adenoviruses 3 and 7, and simian adenovirus M2, M3, and M4 have shown that
residual chlorine of 0.69 mg/L reduced adenovirus type 3 by 99 percent. A concentration of 0.89 mg/L was needed to
achieve the same reduction of adenovirus type 7. Studies of HAV, human rotavirus, poliovirus 1, and adenovirus 5
disinfection in tap water with copper and silver ions and reduced levels of free chlorine have been undertaken. Viruses
were exposed to 1.0, 0.5, or 0.2 mg/L of free chlorine, with and without copper and silver ions. They found that
adenovirus type 5 was more resistant to all disinfection treatments than poliovirus 1, but less resistant than either HAV
or human rotavirus. Depuration of enteric adenovirus 40 from artificially contaminated mussels, in a continuous flow of
ozonated marine water, took much longer than the removal of poliovirus 1. However, it was depurated faster than either
HAV or human rotaviruses.

Comparative ultraviolet (UV) light inactivation studies showed that enterovirus 70 was more susceptible to inactivation
than human adenovirus type 19. It took less than 10 mW/cm /min to register a 4.5-log reduction of the enterovirus 70.
Ultraviolet doses of 60 mW/cm /min were necessary to reach similar levels of inactivation of adenovirus 19. The
comparisons of the resistance of enteric adenoviruses to UV light disinfection with poliovirus type 1 and the coliphages
MS-2 and PRD-1 have been made. The doses of UV to achieve a 90 percent inactivation of adenovirus 40, adenovirus
41, coliphages MS-2 and PRD-1, and poliovirus type 1 were 30, 23.6, 14, 8.7, and 4.1 mW sec/cm2, respectively.

A stroviruses
Currently no methods for isolating astroviruses in cell cultures are routine. Astroviruses were originally isolated from
stools by use of trypsin-treated primary human embryonic kidney (HEK) cells, and CaCo-2 cells can also be used for
viral isolation.

Direct detection of astrovirus antigen or nucleic acid in water has not been reported, but astroviruses have been
isolated in cell cultures from a natural water source. After three blind passages in CaCo-2 cells of a concentrated river
water sample from sites with sewage pollution, astroviruses were detected by nucleic acid hybridization. The findings
were confirmed by reverse-transcription PCR.

No studies concerning resistance to chemical or physical agents have been reported for human astroviruses. It can be
assumed, based on their biophysical and biochemical properties, that they are similar to other gastroenteritis viruses
regarding their stability in the environment. There is one report on isolation of astroviruses from river water.

C aliciviruses
Human caliciviruses currently cannot be routinely cultured in vitro using animal tissues or animal cell lines. Therefore,
detection techniques that do not provide direct evidence of viral infectivity are used. These techniques include visual
detection of viruses by transmission electron microscopy and laboratory tests such as ELISA (enzyme-linked
immunosorbent assay) and RT-PCR (reverse transcriptase-polymerase chain reaction) that detect the constituent viral
proteins and RNA, respectively.

No information exists about the environmental stability of caliciviruses. This information may become available after the
development of in vitro infectivity assays for these viruses.

Human caliciviruses and hepatitis E virus have caused numerous waterborne disease outbreaks. Infections and
outbreaks of illness can occur year-round with some increased incidence of the classical caliciviral illness during the
winter months. Incidence of illness caused by the specie hepatitis E virus tends to peak in autumn in the temperate
areas of the world, while in tropical and monsoon areas, it occurs predominantly in flooded areas during the rainy
season. Among the largest outbreaks have been those in Kashmir, Somalia, and Delhi. The death rates associated with
hepatitis E have varied by a factor of nearly 50, which suggests that the severity of illness caused by this virus may be
strongly strain-dependent. For instance, while the Delhi outbreak was estimated to have resulted in 90 deaths among
97,600 cases of illness, the Somalia outbreak reportedly resulted in nearly the same number of deaths while involving
only 2,000 cases of illness.

Enteroviruses
Enteroviruses have been the most studied of all enteric viruses for their ability to be' removed by water treatment
processes. Enteroviruses appear to be capable of being removed easily by conventional water treatment involving
disinfection (99.99 percent or greater). Coxsackieviruses appear to be more resistant to ultraviolet (UV) light
disinfection than the other enteroviruses.

H epatitis A
HAV is one of the more persistent enteric viruses in the environment. Inactivation rates in feces, sewage,
water, soil, and sediments are so slow that infectious viruses may persist for months to years, especially at
lower temperatures.

Removal of HAV by conventional physicochemical water treatment processes of coagulation—flocculation and filtration
is similar to that of other enteric viruses, with reductions up to 99 percent. Disinfection of water with free chlorine,
chlorine dioxide, ozone, and ultraviolet (UV) light radiation can achieve up to 99.99 percent inactivation of HAV under
optimum conditions. C x T-99.99 values for the chemical disinfectants are less than 20 mg-min/L. If HAV is protected
within organic matter or other particles, however, rates of inactivation can be dramatically reduced and C x T values
can be more than 10-fold higher than for dispersed virions. UV radiation inactivates HAV better than some other enteric
viruses, with 99.99 percent reduction at a dose of less than 20 mW-sec/cm . Like other enteric viruses, HAV is relatively
resistant to combined chlorine. For monochloramine, HAV C x T-99.99 values are in the thousands of mg-min/L. A small
fraction of hepatitis A virions are highly resistant to monochloramine, probably because they are aggregated. Overall,
complete conventional treatment of surface water should reduce HAV by 99.99 percent, as required by the Surface
Water Treatment Rule (SWTR). Under optimum conditions, it should be possible to achieve substantial inactivation of
HAV in groundwater by disinfection processes. However, the numerous groundwater outbreaks of HAV reported in the
United States and elsewhere suggest that current groundwater supplies and their treatment practices (typically
disinfection only) are not always adequate.

R eovirus
No studies that specifically examined reovirus removal during conventional water treatment have been found. However,
no reoviruses were found in the 500- to 1,000-L samples of treated drinking water when levels of reoviruses were
detected in 26 or 66 percent of the raw water samples (100-L) studied. Reovirus removal by slow sand filtration
demonstrated that such treatment can remove up to 99.99 percent (4 logio units) depending on water quality, flow rate,
and bed construction. Adsorbed reovirus was detected throughout the bed, but concentrations decreased with
increasing bed depth. Some work on inactivation of viruses by 0.5 ppm chlorine suggests that 4 logio reduction in
reovirus titer can be achieved after 2 to 4 minutes. The degree of reovirus clumping may have an impact on disinfection
rates.
Most studies of virus removal from wastewater during treatment do not specifically examine reductions for reoviruses.
However, a treatment plant handling domestic sewage removed reoviruses less efficiently than enteroviruses. Studies
isolated reoviruses from chlorinated primary effluent at approximately 50 percent of that isolated from raw sewage.
Dewatering of sludge led to only a small drop in reovirus recovery until sludge solids were greater than 90 percent.

R otaviruses
Currently, the understanding for removal of rotaviruses by conventional water treatment processes is similar to other
enteric viruses. They are effectively removed during the processes, especially through disinfection. Rotaviruses are
susceptible to disinfection in water with free chlorine, ozone, and ultraviolet (UV) radiation. They are more resistant to
inactivation by UV light than enteroviruses, probably because they contain double-stranded RNA.
Most viruses are known to be substantially inactivated by free chlorine, but are more resistant to free chlorine than
most enteric bacteria. Viruses in feces, wastewater, tapwater, and associated with solids are much more resistant to
inactivation.

Small, Round, Structured Viruses (Human Caliciviruses?)
Because SRSVs cannot be grown in cell culture, nothing is known about survival of intact and potentially
infectious SRSVs in the environment. Although SRSVs are unique because their capsid is composed of
only one protein, SRSV resistance to environmental degradation might be similar to other nonenveloped,
single-stranded RNA viruses, such as hepatitis A virus.

Very little information has been reported on the survival characteristics of SRSVs during standard water treatment
processes. In one study, human volunteers were given NV treated with chlorine. A dose of 3.75 mg/L, resulting in no
free residual Cl, failed to inactivate NV. A dose of 10 mg/L, with a free residual Cl level of 5—6 mg/L, apparently did
inactivate the virus. The study concluded that NV was very resistant to Cl as compared to other indicator viruses.
Because an infectivity model has not been developed for SRSVs, the effectiveness of water treatment procedures in
eliminating or inactivating these important human pathogens is difficult to determine. Researchers are attempting to
identify specific human intestinal cells til will support the growth of SRSVs to establish such an infectivity model. Howevt
recent studies using Norwalk virus VLPs in filtration experiments show promise as model systems for enteric virus
transport through treatment processes,