Lower respiratory infections is a category that includes flu (influenza) and lung infections (pneumonia).
Influenza is an infection caused by an Influenza virus. It starts by affecting the upper respiratory tract and makes you generally ill with a fever. When fatal, it has usually progressed to also causing infection of the lower respiratory tract (pneumonia). Periodically there is a worldwide pandemic of influenza. One in 1918 probably killed 50 million people. Many of the extra deaths in an influenza epidemic are attributed to pneumonia and not specifically to influenza. For that reason it is included here within the Lower respiratory infection category, and not with Upper respiratory infections U040.
Pneumonia is an infection of the lung that can be caused by bacteria or viruses. Untreated, especially when caused by bacteria, it is often fatal. Antibiotics have dramatically reduced the number of deaths. Where appropriate treatment is available, death usually occurs only sometimes in the very young, the elderly, people with other diseases or problems such as from past smoking and/or alcoholism.
Infections can cause permanent damage to parts of the lungs, making you more prone to further infections, and impair overall lung function, making you short of breath. Pneumonia is common in the elderly and in people who are malnourished. It is also more common in people with chronic bronchitis U112, often due to smoking; and with lung damage due to working in dusty environments, especially those in mines.
In 2002 Pneumonia caused 16.8% of deaths in children under 15 years old, 2.2% of deaths in adults aged 15 to 59 years and 4.8% of deaths in people over 60 years old, 3.3% of all deaths in rich territories, 3.7% of all deaths in poor territories and 10.0% of all deaths in very poor territories.
Global Burden of Disease estimated in 2002 Pneumonia to cause 5.7% of all Male, 6.0% of all Female, 2.6% of all Poor territory and 8.5% of all Very poor territory burden of disease (Disability Adjusted Lost Years).
Pneumonia caused 6.9% of all deaths worldwide in 2002, an average was 634 deaths per million people per year.