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Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.
Stroke kills people from all ethnic backgrounds, but the people at highest risk for fatal strokes are: black men, black women, Asian men, white men, and white women.
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).