houseflies are a greater menace than earlier believed. A team of microbiologists led by Peter Grubel at St Elizabeth's Medical Centre, Boston, has found that houseflies spread a bacterium called Helicobacter pylori that causes ulcers. They transport the bacterium on their skins and intestinal tracts, and pass it from one person to another (Journal of Clinical Microbiology , Vol 35, No 6).

Ever since Barry Marshall, an Australian scientist discovered that ulcer is caused by H pylori , researchers had been trying to find the source of the bacteria. People infected by the bacterium excrete viable germs. The findings show that houseflies lay eggs, develop and feed on excrement