This is the VOA Special English Health Report.

　　Dengue fever is sometimes called "break-bone fever." It produces intense pain in the muscles and joints and behind the eyes. People get severe headaches. There are no cures, but most people recover, though some take a long time.

　　Dengue is spread through the bite of infected mosquitoes. Four related viruses cause the disease. Recovery from one of them provides lifetime protection only against that virus.

　　Scientists at research centers around the world say they are making progress toward vaccines to protect against dengue fever. Robert Edelman at the University of Maryland is an expert in dengue vaccine research. He says at least two experimental vaccines have moved beyond laboratory tests and are now being tested in people.

　　The World Health Organization currently estimates that there may be fifty million dengue infections worldwide every year. It strikes cities and rural areas mainly in warm, wet climates. It causes physical as well as economic pain.

　　Dengue is now found in more than one hundred countries. About forty percent of the world population is at risk. Southeast Asia and the western Pacific are the most seriously affected. But it also affects Africa, the eastern Mediterranean and the Americas.

　　Doctor Edelman noted that in a severe outbreak this year in Brazil, so many people got sick that hospitals in Rio de Janeiro state had to close. The army set up field hospitals in April and doctors came from other areas to help treat patients. In Vietnam, health officials say patients have sometimes had to share hospital beds because of large numbers of cases.

　　The W.H.O. says dengue is spreading to new areas and producing major outbreaks. Venezuela, for example, reported more than eighty thousand cases last year. These included more than six thousand cases of dengue hemorrhagic fever.

　　Dengue victims sometimes develop bleeding. This is dengue hemorrhagic fever. The W.H.O. says it was first recognized in the nineteen fifties. Today it affects most Asian countries and is a leading cause of serious disease and death in children.

　　Each year an estimated half-million people with dengue hemorrhagic fever require hospital treatment. The W.H.O. says about two and one-half percent die. But people are more likely to die if they do not get help. For now, the W.H.O. says the only way to prevent the spread of dengue fever is to fight the mosquitoes that carry it.

　　And that's the VOA Special English Health Report, written by Jerilyn Watson. I'm Steve Ember.