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As many as 20% of Americans have been infected by the fungus known as Histoplasmosis. While most people are asymptomatic or only have slight symptoms, infection can progress to a rapid and potentially fatal superinfection.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.
Pregnant women usually experience a heightened sense of smell beginning late in the first trimester. Some experts call this the body's way of protecting a pregnant woman from foods that are unsafe for the fetus.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.