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During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
According to the National Institute of Environmental Health Sciences, lung disease is the third leading killer in the United States, responsible for one in seven deaths. It is the leading cause of death among infants under the age of one year.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
In the United States, congenital cytomegalovirus causes one child to become disabled almost every hour. CMV is the leading preventable viral cause of development disability in newborns. These disabilities include hearing or vision loss, and cerebral palsy.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.

