392 ◾ Fundamental Food Microbiology
NoV in cell cultures has not yet been successful; thus various surrogate viruses, murine norovirus
(MNV) and feline calcivirus (FCV), are used as a model to study NoV.
Norovirus transmission occurs primarily from person to person through contacts or aerosolized
vomit, water, and foods contaminated with feces or vomit. Outbreaks are generally associated in
an environment in which large numbers of people are present in close contact, such as in hospitals,
cruise ships, hotels, restaurants, nursing homes, daycare centers, prisons, military installments,
and sports stadiums. Fresh produce, including lettuce, tomato, melons, green onions, strawberries, raspberries, peppers, fresh-cut fruits, and salads, and food handlers, processors, and irrigation
water are also involved in norovirus transmission. Bivalve shellfish, such as oysters, clams, and
mussels, are also the source of foodborne norovirus. The infectious dose of norovirus is very low:
about 10 viral particles. NoVs infect the mature enterocytes covering the intestinal villi leading
to massive cell damage and malabsorption, leading to diarrhea. The gastrointestinal symptoms
include explosive projectile vomiting, nausea, cramps, diarrhea, chills, headache, dehydration,
and a high-grade fever. Adults are more susceptible to norovirus than children and the incubation
period is 24–48 hours. Symptoms appear within 12–24 hours after ingestion and last for one to
two days. The disease is self-limiting and the viruses are excreted in the feces of infected persons
(100 billion virus particles/gram of feces) for a prolonged period of time. NoV is relatively stable in
increasing concentrations of chlorine and temperatures from freezing to 60°C (140°F).
Hepatitis A Virus 6,11
Hepatitis A is a nonenveloped, single-stranded RNA virus and belongs to the Picornaviridae family and Hepatovirus genus. HAV virus is 27–32 nm in diameter and has icosahedral symmetry. It
is grown in mammalian cell cultures but requires a long adaptation period. Annually, 1.4 million
people suffer from HAV infection worldwide. The virus remains stable in the environment for at
least a month and may be resistant to heating and disinfectant, such as chlorine.
Because it is of enteric origin, HAV is excreted in very high numbers in human feces. HAV
also do not multiply outside the human body, including in contaminated foods, because it requires
live human cells to multiply. HAV transmission occurs through contaminated food, water, food
handlers, or direct contact with an infected person. An infectious dose of the virus is very low,
about 10–100 virus particles. Following ingestion of HAV through contaminated food (or other
sources), an individual may or may not develop symptoms. The viruses rapidly move to the liver
and invade hepatocytes. In affected individuals, symptoms occur after approximately four weeks
with a range of two to seven weeks. The general symptoms in the early stage involve fever, malaise,
nausea, vomiting, abdominal discomfort, and inflammation of the liver leading to jaundice at a
later stage. In a jaundiced patient, the feces are pale colored and the urine becomes dark. Anorexia,
vomiting, malaise, and fever are manifested in the hepatitis patients, and virus particles are shed in
large numbers in feces (10 9 particles per gram). Symptoms may last for one to two weeks or longer.
The viruses are shed via feces, generally during the last half of the incubation period. Severity of
the disease is strongly associated with age. Young children display an asymptomatic form of the
disease while young adults and adults show symptomatic disease.
Bovine Spongiform Encephalopathy (BSE) 12
Transmissible spongiform encephalopathy (TSE) is also known as bovine spongiform encephalopathy (BSE) or mad cow disease, scrapie in sheep, Creutzfeldt-Jakob (CJD) or variant CJD (vCJD),
and kuru in humans. In the early 1950s, in the eastern highlands of Papua New Guinea, kuru
NoV in cell cultures has not yet been successful; thus various surrogate viruses, murine norovirus
(MNV) and feline calcivirus (FCV), are used as a model to study NoV.
Norovirus transmission occurs primarily from person to person through contacts or aerosolized
vomit, water, and foods contaminated with feces or vomit. Outbreaks are generally associated in
an environment in which large numbers of people are present in close contact, such as in hospitals,
cruise ships, hotels, restaurants, nursing homes, daycare centers, prisons, military installments,
and sports stadiums. Fresh produce, including lettuce, tomato, melons, green onions, strawberries, raspberries, peppers, fresh-cut fruits, and salads, and food handlers, processors, and irrigation
water are also involved in norovirus transmission. Bivalve shellfish, such as oysters, clams, and
mussels, are also the source of foodborne norovirus. The infectious dose of norovirus is very low:
about 10 viral particles. NoVs infect the mature enterocytes covering the intestinal villi leading
to massive cell damage and malabsorption, leading to diarrhea. The gastrointestinal symptoms
include explosive projectile vomiting, nausea, cramps, diarrhea, chills, headache, dehydration,
and a high-grade fever. Adults are more susceptible to norovirus than children and the incubation
period is 24–48 hours. Symptoms appear within 12–24 hours after ingestion and last for one to
two days. The disease is self-limiting and the viruses are excreted in the feces of infected persons
(100 billion virus particles/gram of feces) for a prolonged period of time. NoV is relatively stable in
increasing concentrations of chlorine and temperatures from freezing to 60°C (140°F).
Hepatitis A Virus 6,11
Hepatitis A is a nonenveloped, single-stranded RNA virus and belongs to the Picornaviridae family and Hepatovirus genus. HAV virus is 27–32 nm in diameter and has icosahedral symmetry. It
is grown in mammalian cell cultures but requires a long adaptation period. Annually, 1.4 million
people suffer from HAV infection worldwide. The virus remains stable in the environment for at
least a month and may be resistant to heating and disinfectant, such as chlorine.
Because it is of enteric origin, HAV is excreted in very high numbers in human feces. HAV
also do not multiply outside the human body, including in contaminated foods, because it requires
live human cells to multiply. HAV transmission occurs through contaminated food, water, food
handlers, or direct contact with an infected person. An infectious dose of the virus is very low,
about 10–100 virus particles. Following ingestion of HAV through contaminated food (or other
sources), an individual may or may not develop symptoms. The viruses rapidly move to the liver
and invade hepatocytes. In affected individuals, symptoms occur after approximately four weeks
with a range of two to seven weeks. The general symptoms in the early stage involve fever, malaise,
nausea, vomiting, abdominal discomfort, and inflammation of the liver leading to jaundice at a
later stage. In a jaundiced patient, the feces are pale colored and the urine becomes dark. Anorexia,
vomiting, malaise, and fever are manifested in the hepatitis patients, and virus particles are shed in
large numbers in feces (10 9 particles per gram). Symptoms may last for one to two weeks or longer.
The viruses are shed via feces, generally during the last half of the incubation period. Severity of
the disease is strongly associated with age. Young children display an asymptomatic form of the
disease while young adults and adults show symptomatic disease.
Bovine Spongiform Encephalopathy (BSE) 12
Transmissible spongiform encephalopathy (TSE) is also known as bovine spongiform encephalopathy (BSE) or mad cow disease, scrapie in sheep, Creutzfeldt-Jakob (CJD) or variant CJD (vCJD),
and kuru in humans. In the early 1950s, in the eastern highlands of Papua New Guinea, kuru