Disease detectives say they are seeing welcome progress in tracking down some of the deadliest food-borne pathogens after several spectacular outbreaks in recent years. However, food safety experts say the war against food pathogens is far from over. As progress is made in fighting pathogens on one front, new problems and pathogens crop up elsewhere.

Within the last year, Scripps Howard News Service reports, the US saw the biggest outbreak of Hepatitis A, a disease once thought confined to poor countries with inadequate sanitation. Some 540 people in Pennsylvania were infected and three died after eating green onions. Meanwhile, outbreaks of the Norwalk virus beached some luxury cruises, and a dangerous strain of E. coli showed up at a Florida petting zoo.

Food scientists say these examples show it’s hardly the time for cooks to relax safe handling procedures for raw meats and vegetables as the warmer weather signals the beginning of the peak season for food poisoning.