QUESTION: If you have had pneumonia, do you become more prone to respiratory infections, including the common cold?
ANSWER: Respiratory infections affect two main areas in the body. Infections such as the common cold affect the upper respiratory tract, which includes the nose, sinuses, pharynx and larynx. Infections such as pneumonia affect the lower respiratory tract, primarily involving the lungs.
A healthy individual who gets pneumonia is not necessarily prone to other respiratory infections, including the cold.
Having said that, if an individual has certain underlying health conditions, he or she may be prone to respiratory infections in general. Conditions such as asthma, cystic fibrosis or immune suppression from chemotherapy, for example, may place people at higher risk.
Influenza is an infection that is usually limited to the upper respiratory tract. However, in severe cases, both the upper and lower respiratory tract can be affected. This is a key concern, and there is ample evidence that influenza may be complicated by secondary bacterial pneumonia.
Recent studies have shown a pattern of what we call "bacterial super-infection." Bacterial pneumonia following flu was probably the cause of most of the deaths among individuals infected in the 1918 Spanish influenza pandemic. And about 30 per cent of cases of severe H1N1 flu in 2009 probably involved bacterial super-infection.
In order to avoid complications of influenza, it's best to reduce your risk of getting infected with the virus. Diligent hand washing and annual vaccination are key to flu prevention and control. Both these actions will better protect you and your loved ones, particularly the very young and the elderly, who are much more vulnerable.
Samira Mubareka is a physician and virologist at the Sunnybrook Health Sciences Centre in Toronto. Part of her research involves the study of the influenza virus and its interactions with bacterial pathogens.