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The CDC is warning that malaria is spreading locally in the United States. Cases have been seen in Texas and Florida, the first documented cases of local transmission in 20 years. The disease is most commonly spread by mosquitoes but can also be spread through blood transfusions, organ transplants, needle-sharing and from mother to fetus. While rare in the U.S., there are more than 240 million cases of malaria worldwide each year, the vast majority in Africa. Symptoms can include fevers, chills, headache and fatigue.