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Vampire bats have a natural anticoagulant in their saliva that permits continuous bleeding after they painlessly open a wound with their incisors. This capillary blood does not cause any significant blood loss to their victims.
During pregnancy, a woman is more likely to experience bleeding gums and nosebleeds caused by hormonal changes that increase blood flow to the mouth and nose.
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.
About 3.2 billion people, nearly half the world population, are at risk for malaria. In 2015, there are about 214 million malaria cases and an estimated 438,000 malaria deaths.
The first successful kidney transplant was performed in 1954 and occurred in Boston. A kidney from an identical twin was transplanted into his dying brother's body and was not rejected because it did not appear foreign to his body.