The winter months of the year are sometimes referred to as "the cold and flu season" due to an increased incidence of respiratory illness.
Viral diseases due to parainfluenza viruses, adenoviruses, rhinoviruses, and certain other viruses that affect the respiratory tract are really "the flu". Illness due to parainfluenza viruses is characterized by fever and one or more symptomatic reactions such as chills or chilliness, headache, general aching, malaise, and loss of appetite, and occasionally in infants, gastrointestinal disturbances. Various areas of the respiratory tract are affected, as evidenced by the presence of any one or a combination of rhinitis, sore throat, tonsilitis, bronchitis, and possible pneumonia. The incubation period for this type of illness is from 1 to 10 days. The illness usually subsides in 2 to 5 days; however complications of sinusitus, bronchitis, and pneumonia may occur. Flu vaccines have been developed that can provide immunity to certain designated flu viruses if obtained annually.
Symptoms of the common cold are more uncomfortable than severe. These symptoms are usually confined to a stuffy nose and cough. With no complications, cold symptoms usually disappear within a week to 10 days.
The following table compares symptoms of viral flu with the common cold.
Fever: 100 - 104°F
Loss of appetite
People also complain of "stomach flu", especially during the holiday season. This is most likely due to a foodborne gastrointestinal illness of either viral or bacterial origin. It is not a respiratory illness.
A recent CDC report suggests that 67% of foodborne illnesses are of viral origin, of which the Norwalk virus is the common agent (Mead et al., 1999). The following description characterizes the symptoms of illness due to Norwalk or Norwalk-like viruses. The median incubation period ranges from 24 to 48 hours. The median duration times are 12 to 60 hours. A high percentage of patients have symptoms of diarrhea, nausea, and abdominal cramps. About 1/3 of ill individuals report fever. Children and adolescents are likely to experience vomiting more frequently than diarrhea, while adults experience higher rates of diarrhea than of vomiting. This combination of incubation period, duration of illness, and relative frequency of reported symptoms is not like those associated with outbreaks of bacterial infection or intoxication. Stool cultures are negative for bacterial pathogens (Hedburg and Osterholm, 1993).
Another common feature of outbreaks of foodborne illness due to Norwalk-like viruses is the likelihood of secondary transmission to household members who were not exposed to an implicated food or water source.
Frequent and thorough hand washing and drying is the best way to minimize the likelihood of contracting or transmitting these types of viral illnesses.
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