Viruses and Some Other Proven and Suspected Foodborne Biohazards 731
and cockles were incriminated.
4 The incubation period was 24–30 hours, and from 12 of 14 stool
samples, small, round virus particles measuring 25–26 nm in diameter were demonstrated, but they
were not found in cockles. Although the investigators believed that the agents were neither Norwalk
nor Hawaii, these outbreaks are regarded by some as Norwalk virus outbreaks. The 1978 outbreak in
Australia that involved at least 2,000 persons was well documented, and the vehicle food was oysters.
74
The virus was found in 39% of fecal specimens examined by electron microscopy, and antibody responses were demonstrated in 75% of paired sera tested. The incubation period ranged from 18 to
48 hours, with most cases occurring in 34–38 hours. Nausea was the first symptom, usually accompanied by vomiting, nonbloody diarrhea, and abdominal cramps, with symptoms lasting 2–3 days.
Another outbreak in Australia was traced to bottled oysters and symptoms occurred in 24–48 hours.
36
The oysters had an APC of 2.2 × 10
4 /g and a fecal coliform count of 500/100 g. The first documented
food source outbreaks in the United States are those that occurred in New Jersey in 1979, where lettuce
was the vehicle food, and the Florida outbreak in 1980 that was traced to raw oysters. In the latter, the
agent was identified by a radioimmunoassay method.
Rotaviruses
The first demonstration of these viruses occurred in 1973 in Australia, and they were first propagated
in the laboratory in 1981. Six groups have been identified, and three are known to be infectious for
humans. Group A is the most commonly encountered among infants and young children throughout
the world. Group B causes diarrhea in adults, and they have been seen only in China. Rotaviruses
belong to the family Reoviridae; they are about 70 nm in diameter, are nonenveloped, and contain
double-stranded RNA (dsRNA). The fecal–oral route is the primary mode of transmission.
Rotaviruses cause an estimated one-third of all hospitalizations for diarrhea in children below age
5, and the peak season for infection occurs during the winter months. Most susceptible are children
between the ages of 6 months and 2 years, and it has been reported that virtually every child in the
United States is infected by age 4.
24 Although most persons are immune by age 4, high inoculum
or lowered states of immunity can lead to milder illness among older children and adults.
24 These
viruses are known to be transmitted among children in day care centers and by water. A community
waterborne outbreak occurred in Eagle-Vail, Colorado, in 1981, and 44% of 128 persons, most of them
adults, became ill.
49 They are believed to be only infrequent causes of foodborne gastroenteritis.
30
The incubation period for rotavirus gastroenteritis is 2 days. Vomiting occurs for 3 days accompanied
by watery diarrhea for 3–8 days, and often abdominal pain and fever also occur.
24 They are known to
be associated with travelers’ diarrhea. It appears that these viruses induce diarrhea by activating the
enteric nervous system (ENS) based on the inhibition of ENS functions in mice and in vitro by four
drugs that inhibit ENS functions.
70
For the 23-month period between January 1989 and November 1990, 48,035 stool specimens were
examined in the United States, with 9,639 (20%) being positive for rotavirus.
22 The highest percentage
of positive stools occurred in February (36%) and the lowest in October (6%). Between 1979 and 1985,
an annual average of 500 children died from diarrheal illness in the United States, and 20% were caused
by rotavirus infections.
22
The host-cell-receptor protein for rotavirus also serves as the β-adrenergic receptor. Once inside
cells, they are transported to lysosomes where uncoating occurs.
Rotaviral infections can be diagnosed by immunoelectron microscopy, RT–PCR, enzyme-linked
immunosorbent assay (ELISA), and latex agglutination methods.
and cockles were incriminated.
4 The incubation period was 24–30 hours, and from 12 of 14 stool
samples, small, round virus particles measuring 25–26 nm in diameter were demonstrated, but they
were not found in cockles. Although the investigators believed that the agents were neither Norwalk
nor Hawaii, these outbreaks are regarded by some as Norwalk virus outbreaks. The 1978 outbreak in
Australia that involved at least 2,000 persons was well documented, and the vehicle food was oysters.
74
The virus was found in 39% of fecal specimens examined by electron microscopy, and antibody responses were demonstrated in 75% of paired sera tested. The incubation period ranged from 18 to
48 hours, with most cases occurring in 34–38 hours. Nausea was the first symptom, usually accompanied by vomiting, nonbloody diarrhea, and abdominal cramps, with symptoms lasting 2–3 days.
Another outbreak in Australia was traced to bottled oysters and symptoms occurred in 24–48 hours.
36
The oysters had an APC of 2.2 × 10
4 /g and a fecal coliform count of 500/100 g. The first documented
food source outbreaks in the United States are those that occurred in New Jersey in 1979, where lettuce
was the vehicle food, and the Florida outbreak in 1980 that was traced to raw oysters. In the latter, the
agent was identified by a radioimmunoassay method.
Rotaviruses
The first demonstration of these viruses occurred in 1973 in Australia, and they were first propagated
in the laboratory in 1981. Six groups have been identified, and three are known to be infectious for
humans. Group A is the most commonly encountered among infants and young children throughout
the world. Group B causes diarrhea in adults, and they have been seen only in China. Rotaviruses
belong to the family Reoviridae; they are about 70 nm in diameter, are nonenveloped, and contain
double-stranded RNA (dsRNA). The fecal–oral route is the primary mode of transmission.
Rotaviruses cause an estimated one-third of all hospitalizations for diarrhea in children below age
5, and the peak season for infection occurs during the winter months. Most susceptible are children
between the ages of 6 months and 2 years, and it has been reported that virtually every child in the
United States is infected by age 4.
24 Although most persons are immune by age 4, high inoculum
or lowered states of immunity can lead to milder illness among older children and adults.
24 These
viruses are known to be transmitted among children in day care centers and by water. A community
waterborne outbreak occurred in Eagle-Vail, Colorado, in 1981, and 44% of 128 persons, most of them
adults, became ill.
49 They are believed to be only infrequent causes of foodborne gastroenteritis.
30
The incubation period for rotavirus gastroenteritis is 2 days. Vomiting occurs for 3 days accompanied
by watery diarrhea for 3–8 days, and often abdominal pain and fever also occur.
24 They are known to
be associated with travelers’ diarrhea. It appears that these viruses induce diarrhea by activating the
enteric nervous system (ENS) based on the inhibition of ENS functions in mice and in vitro by four
drugs that inhibit ENS functions.
70
For the 23-month period between January 1989 and November 1990, 48,035 stool specimens were
examined in the United States, with 9,639 (20%) being positive for rotavirus.
22 The highest percentage
of positive stools occurred in February (36%) and the lowest in October (6%). Between 1979 and 1985,
an annual average of 500 children died from diarrheal illness in the United States, and 20% were caused
by rotavirus infections.
22
The host-cell-receptor protein for rotavirus also serves as the β-adrenergic receptor. Once inside
cells, they are transported to lysosomes where uncoating occurs.
Rotaviral infections can be diagnosed by immunoelectron microscopy, RT–PCR, enzyme-linked
immunosorbent assay (ELISA), and latex agglutination methods.