How Contagious are Respiratory Tract Infections?

It's cold and flu season. Your co-worker in the next cubicle has a mound of Kleenex on his desk, obviously nursing a cold. Following a sneezing fit, you can practically see the germs coming over the cubicle wall seeking someone else to infect. With the common wintertime illnesses, what is your likelihood of becoming infected through exposure such as this? Are there ways of minimizing the risk of becoming infected?


One of the most common (and preventable) wintertime illnesses is influenza. Flu is typically spread via direct exposure to droplets from coughs or sneezes of someone with the illness. Homes, schools, dormitories, and areas with poor ventilation or recirculated air (such as commercial airplanes) are the places of highest risk for contracting this disease. There is a 20%-60% risk of contracting the disease from a family member with influenza.

Strep throat, caused by the Streptococcus bacteria, is a common cause of severe sore throat, particularly in children. Fortunately, this illness is less contagious than many of the viral upper respiratory tract infections. Spread occurs through close contact with an infected person. Sharing personal items, eating implements or a drinking glass with someone with an infection can lead to spread. Strep throat can also be spread through droplets released from coughing or sneezing. The likelihood of strep throat spreading to another family member is around 10%. Its spread is highly unlikely in the work situation.

The common cold is caused a group of viruses known as Rhinoviruses. Colds are spread either by direct contact with an ill person, breathing in droplets from coughs or sneezes, or from contact with tissues, linens, or other surfaces holding the virus. This group of viruses is highly contagious. It is estimated that family members have a 66% chance of contracting a cold from someone with the illness.

A particular concern among children are infections caused by Respiratory Syncytial Virus (RSV). This is a leading cause of bronchial infections and pneumonia in infants and children. Schools and day care centers are the places of highest risk for contracting this illness. RSV is spread from respiratory secretions through close contact with infected persons or contact with contaminated surfaces or objects. Significant exposure practically guarantees the development of this illness, although its severity is highly variable.

The most common type of bacterial pneumonia in adults is Streptococcus pneumoniae (pneumococcus). Spread of this illness usually occurs through direct contact with an ill individual or by breathing in droplets released from coughing or sneezing. Causal exposure to someone with pneumococcal pneumonia is very unlikley to result in spread of the disease. The exception to this may be in someone who can not fight infections normally.

There is a vaccine available to protec those at risk from contracting this disease. There are a number of things that you can do to help prevent spread of these infections:

• Avoid close contact with people who are ill with one of these infections.
• Unless ventilation is good, try to avoid shared space with people who are coughing or sneezing.
• Wash your hands after greeting someone with a viral infection.
• Encourage children to wash their hands. Kids are more likely than adults to spread infection within a family.

Sometimes it seems inevitable that an upper respiratory tract infection will develop at some point during the cold and flu season. As you gather with friends and family during the holiday season, proper sanitation and immunization practices will help you avoid the spreading of many of the more serious of these infections.