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Influenza, a viral illness with peak infectivity between December and February, causes fever, cough, rhinitis, myalgias, and abdominal complaints frequently in the pediatric population.
Influenza vaccination can reduce the risk of mortality in high risk patients by 50% and by 65% in healthy children.
Rapid influenza diagnostic test (RIDT) positive predictive values are dependent on influenza prevalence. Positive results outside of peak season should be interpreted cautiously by the physician.
There is a lack of evidence supporting the routine treatment with antiviral medications for low-risk healthy children with influenza infection.
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Annually, during the winter months emergency departments (EDs) experience higher patient volumes attributed to viral illnesses. In temperate climates across the northern hemisphere, this is the season associated with influenza infection, with peak activity between December and February. An average of 10% to 40% of healthy children are infected with influenza every season.1,2 This rate varies slightly based on strain prevalence and vaccine efficacy. About 1 in 1000 children infected with influenza will require hospitalization, with those less than 6 months old requiring admission at a greater rate.2–4 Death rates vary annually based on the severity of the strain, and are highest among adults greater than 65. On average, 100 children die in the United States from influenza infection every year, with 0.2 deaths for every 100,000 children. In comparison, there are typically 5000 flu-related fatalities each year in adults, with 1.5 deaths per 100,000 people of age between 19 and 65 years, and even higher rates among those above 65 years of age.5,6
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Adults and adolescents will present with “classic” flu symptoms, including sudden onset of fever, malaise, headache, pharyngitis, and myalgias. Children may present with a wider array of symptoms, especially abdominal complaints such as nausea, vomiting, diarrhea, and abdominal pain, while infants can present with viral sepsis, croup, or bronchiolitis. In all pediatric populations, fever and cough are the most common symptoms associated with influenza infection (see Table 64-1).7–12 Once exposed to the virus, replication occurs in the respiratory epithelium. It is then spread via respiratory droplets, either by direct transmission to a person or from a contaminated surface. After exposure, it can take anywhere from 1 to 4 days (on average, 2) for symptoms to develop. The general population is contagious 1 day prior and up to 1 week after symptom onset. However, children and immunocompromised hosts can be contagious for longer periods, with viral shedding lasting up to 14 days.
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