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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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.
More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.
Adults are resistant to the bacterium that causes Botulism. These bacteria thrive in honey – therefore, honey should never be given to infants since their immune systems are not yet resistant.
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.