Seasonal Influenza
Each winter in the United States, seasonal flu imposes a heavy burden on society. About 5–20 percent of the population gets the flu, more than 200,000 people are hospitalized with complications, and about 36,000 people die. Consider this: For every person that dies of influenza each year, the cost to our society is between $1,019,536 (ages 0–19) and $74,146 (age 65+). Add to that the costs of 226,000 influenza-related hospitalizations at costs ranging from $3,366 to $7,653 — and those patients who self-treat at home with over-the-counter medications or who access outpatient care cost the system between $200 and $500.
Influenza is caused by RNA viruses belonging to the Orthomyxoviridae family. Viruses are classified according to the composition of their nuclear proteins into three types: A, B, and C. Influenza C is not monitored by surveillance systems, causes mild or asymptomatic illness, and is of minimal public health impact.
New strain variants that reinfect people throughout life are created by a continuous evolving process, called antigenic drift, resulting from modifications in the viral surface glycoproteins Hemagglutinin (H) and Neuraminidase (N). Small drifts cause yearly outbreaks. Large drifts cause epidemics every few years. Type B viruses have a lesser propensity for antigenic change, cause less severe and less extensive outbreaks, and do not have a reservoir in animal hosts. Type A viruses causes potentially severe illness, is highly mutable, infects both humans and animals, and is responsible for epidemics and pandemics.
In adults symptoms can present as high fever, headache, extreme fatigue, muscle aches, dry cough, sore throat and nasal congestion. Complications can include bacterial pneumonia, dehydration and worsening of chronic medical conditions such as congestive heart failure, asthma and diabetes. Children may also present with vomiting and diarrhea. Complications in children can include sinus problems and ear infections.
The common cold is often mistaken for the flu. The key differences are that the common cold targets only the upper respiratory tract, comes on gradually, a fever if any is low grade, and more prominent symptoms of sore throat, stuffy or runny nose, and sneezing are present.
The flu virus is spread through respiratory droplets released by coughing and sneezing. People can also become infected after touching contaminated surfaces and subsequent transfer to the mouth or nose. Person-to-person infection can occur one day before symptoms and up to five days after illness.
Individuals at high risk for serious complications and yearly vaccination recommended include adults 65 years and older, pregnant women, all children 6 to 23 months of age, children 6 months to 18 years on long-term aspirin therapy, residents of long-term care facilities, adults and children six months and older with chronic medical conditions such as diabetes, kidney disease, asthma, or weakened immune system. Yearly vaccination is also recommended for any person in close contact with someone in a high-risk group such as healthcare workers and caregivers.
The best way to prevent disease transmission includes covering your cough, washing your hands, staying home from school or work when ill, and yearly vaccination.