Laughing Malady Puzzle in Africa 1,000 Along Lake Victoria Afflicted in 18 Months -- Most are Youngsters Schools Closed Down New Illness Produces Fits Lasting Up to an Hour -- No Clue to Origin Found By Robert Conley Special to the New York Times NAIROBI, Kenya, Aug. 7 -- A new ailment on the shores of Lake Victoria has scientists puzzled. It is an epidemic of laughing sickness that produces symptoms bordering on hysteria. The cause is unknown. More than 1,000 Africans have come down with this disease in the last 18 months. Most of them were youngsters. Whole schools have been closed because of the outbreak, which seems to be centered on the village of Bukoba in western Tanganyika. Near Bukoba an entire village fell ill in a matter of days. Investigators have found no trace of fever, but they noticed that the pupils of the suffers' eyes became dilated and that victims were unfit to work for weeks after contracting the disease. To villages with tears their eyes from fits of hysteria, the disease is "endwara ya Kucheka" -- the laughing trouble. To doctors, it is one of African's newest and most puzzling illnesses. Dr. A. H. Rankin of Makerere College in Uganda and R. J. Phillip, medical officer in Bukoba concede that they are completely baffled. In a recent issue of the Central African Medical Journal they report that victims are usually schoolchildren from villages close to Lake Victoria. The Lake is bounded by Kenya, Uganda, and Tanganyika. Bukoba is on the western shore of the lake, about 25 miles South of the Uganda border. Whatever the cause, the ailment appears to be transmitted from person to person. Shortly after contact with a sufferer, the new victim begins to laugh. Soon he is crying, and seizures may last as long as an hour. He begins to feel restless, uneasy. Eventually he beings to lose his powers of concentration. Some victims complain that strange things are moving around in their heads. Tests have made for food poisoning, but all turned out negative. Possible infections by a virus or bacterium cannot be substantiated either. Dr. Rankin's only explanation for the epidemic is that the area around Bukoba may be suffering form mass hysteria. His theory has not yet been ruled out. In recent times medical authorities have recorded similar outbreaks of hysteria in Britain and the United States. During the Middle Ages whole towns in Germany and Italy were ravaged by something called "the dancing mania," which was thought to be a consequence of Black Plague. No Explanation Known American Scientists ho have been in the Nairobi area recently, or have been in correspondence with colleagues there, said yesterday that they were just as puzzled as the physicians in Africa over the laughing sickness. None had heard of the ailment. A possible explanation for the outbreak might be found in investigations that have been made concerning a far more serious laughing sickness. It is called guru and afflicts mainly a single tribe -- the Fores -- in New Guinea. Guru is inevitably fatal. It's victims are almost always women. There is strong evidence that kuru has a hereditary cause. Yet scientists have a hard time explaining how this could be the only factor because in that case the disease, which apparently cropped up 40 years ago, should have become less rather than more prevalent in time. That is what happens with most lethal genetic disorders. One reasonable explanation for kuru's having become more prevalent was suggested in the July 20 issue of the The Lancent, a British medical periodical: Some new environmental factor that favors expression of the otherwise masked and innocuous genetic train may be responsible.