Typhoid fever remains a common, serious and increasingly difficult to treat disease in developing countries. Control measures, such as safe drinking water, and food, and effective sewage, are not likely to be available soon in many of these countries. In the early 1990's most Salmonella typhi from the Mekong Delta region were resistant to chloramphenicol and ampicillin and treatment required new antibiotics such as ciprofloxacin. Now, resistance of S. typhi has spread to ciprofloxacin.