By Dr. John Cannell

Respiratory tract infections involve a large number of infectious diseases in the respiratory tract. They are split into upper respiatory tract infections (URTI) or lower respiratory tract infections (LRTI). LRTI, such as pneumonia, tend to be far more serious conditions than URTI, such as the common cold.

Typical symptoms of URTI include tonsillitis, sore throat, laryngitis, sinusitis, ear infections, and the common cold. Other symptoms can include cough, sore throat, runny nose, nasal congestion, headache, low-grade fever, facial pain or pressure and sneezing.

LRTI are much more serious and are the leading cause of death among all infectious diseases. The two most common types are bronchitis and pneumonia. Cough, chest pain and fever are the common symptoms. Influenza infections affect both the upper and lower respiratory tracts, but the much more dangerous strains, such as H1N1, infect deep into the lower lungs causing severe symptoms. Besides cough and fever, prostration is a prominent symptom of a true influenza infection. An H1N1 influenza strain killed up to 50,000,000 people in 1918 and 1919, and, for unknown reasons, was especially fatal for young people in the prime of life.

Recently, Dr. Jaykaran Charan and colleagues of the Indian Institute of Public Health published a meta-analysis of all randomized controlled trials of vitamin D and respiratory tract infections.

They found five studies that met their criteria, but their paper went to the reviewers before publications of the two most recent randomized controlled trials, one of which was positive (4,000 IU/day for a year) and one of which was negative (100,000 IU/month for 18 months).

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