Introduction

Upper respiratory tract infections affect the airways in the nose, ears, and throat.

Structures of the throat include the esophagus, trachea, epiglottis, and tonsils.

The infections can be caused by viruses, bacteria, or other microscopic organisms. In most cases, these infections lead to colds or mild influenza (flu) and are temporary and harmless. In rare cases, flu can be severe, or the infections may turn into pneumonia.

Organisms that cause these upper respiratory tract infections are generally spread by:

• Direct contact (such as hand-to-mouth)
• Coughing or sneezing

The Common Cold

The common cold (medically known as infectious nasopharyngitis) is the most common upper respiratory tract infection. More than 200 viruses can cause colds. The most common cause is the rhinovirus, which is responsible for about half of all colds. Symptoms usually develop 1 - 3 days after being exposed to the virus.

A cold usually progresses in the following manner:

• It nearly always starts rapidly with throat irritation and stuffiness in the nose.
• Within hours, full-blown cold symptoms usually develop, which can include sneezing, mild sore throat, fever, minor headaches, muscle aches, and coughing.
• Fever is low-grade or absent. In small children, however, fever may be as high as 103?°F for 1 or 2 days. The fever should go down after that time, and be back to normal by the 5th day.
• Nasal discharge is usually clear and runny the first 1 - 3 days. It then thickens and becomes yellow to greenish.
• The sore throat is usually mild and lasts only about a day. A runny nose usually lasts 2 - 7 days, although coughing and nasal discharge can persist for more than 2 weeks.

The adenovirus family causes upper respiratory infections (it is one of the many viruses that cause the common cold). It also causes pneumonia, conjunctivitis, and several other diseases. A newer strain of adenovirus has resulted in several deaths.

Influenza ("The Flu")

Every year, influenza strikes millions of people worldwide. Influenza epidemics are most serious when they involve a new strain, against which most people around the world are not immune. Such global epidemics (pandemics) can rapidly infect more than one fourth of the world's population. For example, the Spanish flu in 1918 and 1919 killed an estimated 20 million people in the U.S. and Europe and 17 million people in India. With modern society's dependence on air travel, an influenza pandemic could potentially inflict catastrophic damage on human lives, and disrupt the global economy.