Viral upper respiratory infections come in every degree of severity and cause symptoms in the ears, sinuses, throat and nose. This report will cover two of the most common respiratory infections: the common cold and influenza (the flu).

The Upper Respiratory Tract

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In the United States the broad category of viral respiratory illness is responsible for much of the school and work-related absenteeism.

Influenza travels around the globe in yearly winter epidemics of varying magnitude. Major epidemics occur every 10-15 years and may kill upwards of 40,000 people in the United States alone each year. Minor epidemics kill "only" about 20,000 in an average year. Most of the deaths occur in people weakened by chronic illnesses, such as heart and respiratory diseases.

The Common Cold
The common cold is characterized by nasal congestion, a runny nose, sneezing and perhaps a sore throat, headache and malaise (not feeling well). A fever is unusual. Symptoms resolve on their own usually within 1-2 weeks.

There are at least 200 known viruses responsible for the symptoms of a common cold. Some of these may also affect the lower respiratory tract and cause other conditions. For instance, respiratory syncytial virus can cause severe pneumonia in infants.

Influenza
Influenza is a very specific illness caused by a single group of influenza viruses. It has a characteristic seasonal cycle that peaks in the winter. It also has typical symptoms, although they vary greatly in severity among cases. It may feel similar to a common cold, but it usually causes a high fever (102°F-104°F), significant malaise, and a dry cough along with a runny nose, headache, muscle ache, and sore throat.

Influenza viruses are divided into three species: A, B, and C. Influenza A is the cause of the worst epidemics. This is because it changes its identity often, so that a person’s previously developed immunity does not recognize the new variation.

International organizations like the World Health Organization (WHO) Epidemic and Pandemic Alert and Response (CSR) team are constantly searching the world for new variations of influenza viruses. Each year they attempt to identify the strains most likely to cause epidemics and make recommendations for developing vaccines against them.