Respiratory tract infection - Is it contagious?
"Stay away from me! I don't want to get sick, too." Most of us have had to utter those words to a family member, friend, or colleague who was sneezing or coughing incessantly. But how do we know how great the chances of catching someone's cold or other illness really are? A medical review published in the New England Journal of Medicine tells us when to exercise concern over eight respiratory tract infections.
Illness(Infectious agent) |
How it gets transmitted |
Places of highest risk |
Percent risk of infection |
|
Bronchiolitis (Respiratory Syncytial Virus, RSV) |
Direct contact with ill person, large-droplets from coughs or sneezes, contact with tissues, linens, or other surfaces holding the virus |
Homes, day-care centers |
In day-care centers, 100% of exposed children become ill, previous infection somewhat lowers the risk |
|
Flu (Influenza viruses) |
Direct contact with ill person, large- and tiny-droplets from coughs or sneezes |
Homes, schools, bars, dormitories, areas with poor ventilation or recirculated air |
20%-60% from a family member, only half of those infected will have symptoms of influenza |
|
The common cold (Rhinovirus) |
Direct contact with ill person, large-droplets from coughs or sneezes, contact with tissues, linens, or other surfaces holding the virus |
Homes, dormitories |
66% from a family member |
|
Tuberculosis |
Tiny-droplets from coughs or sneezes |
Homes, bars, dormitories, nursing homes, areas with poor ventilation |
25%-50% with close contact with a person with active disease, prolonged exposure is usually required |
|
Upper respiratory illness (Adenoviruses) |
Direct contact with ill person, large- and tiny-droplets from coughs or sneezes |
Camps, schools, military camps |
10% of those exposed may become ill, 40% among children, many infected individuals show no symptoms and infection leads to immunity from future infection |
|
Strep throat, scarlet fever (Group A Strep) |
Direct contact with ill person, large-droplets from coughs or sneezes |
Homes |
10% from a family member |
|
Bacterial meningitis (Neisseria meningitides) |
Direct contact with ill person, large-droplets from coughs or sneezes |
Homes, schools, camps |
2%-3% for a child whose sibling has active illness, 0.2%-0.4% for household contacts of the ill child, more than 95% of the time a second case of the disease does not follow a first. |
|
Pneumococcal pneumonia (Streptococcus pneumoniae) |
Direct contact with ill person, large-droplets from coughs or sneezes |
Day-care centers, homeless shelters, camps, prisons, nursing homes |
Generally not regarded as contagious, risk of infection depends on one's general health |
You can do a number of things to help prevent infection:
- Avoid close contact with people who are ill with infections spread through large-droplets.
- Unless ventilation is good, avoid shared space with people who are ill with infections spread through tiny-droplets.
- Wash your hands after greeting someone with a viral infection or after handling an object held by someone infected with Bronchiolitis or a cold.
- Encourage children to wash their hands. Kids are more likely than adults to spread infection within a family.
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