2014英语四级听力练习慢速4.1(2)_大学英语听力

2014英语四级听力练习慢速4.1(2)

　　Signs of the disease appear in victims 10 to 15 days after they are bitten. People with malaria develop a high body temperature. They also can become weak, violently expel material from the stomach, and suffer pain in the head or muscles. If not treated, malaria can make the victim sick and even cause death.

　　A parasite called plasmodium falciparum is responsible for most malaria infections. But experts say a lesser-known form of the disease could become a more serious threat in the future. They are seeing an increase in infections from the plasmodium vivax parasite.

　　An estimated 2.5 billion people live in areas where plasmodium vivax is common. Until recently, experts believed 95 percent of the at-risk population in some areas was protected from vivax infection. This was because they lack a protein in their red blood cells called a Duffy protein. Without it, vivax parasites cannot enter the blood cells. But researchers have found that in Madagascar, people without the Duffy protein may be carrying the vivax parasite. They say it appears the parasite may be changing so it can fight off natural resistance and infect blood cells that lack the Duffy protein.

　　Worldwide Fight Against Malaria Appears to Be Succeeding

　　Researchers remain concerned about the rising number of vivax malaria cases. But the worldwide effort against malaria appears to be succeeding. The World Health Organization recently reported that millions of lives have been saved since 2000 with better prevention and better medicines. And health officials expect even more success as governments and private groups target African countries like Kenya.