Specialist Jelena Kovalkova looks at a petri dish as she works to isolate the Escherichia coli (E.coli) bacteria strain at the Institute of Food Safety, Animal Health and Environment in Riga June 9, 2011. More than 1,600 people have been infected by a toxic strain of E.coli bacteria that has killed at least 17 and may be the deadliest yet in human history. Latvian government officials on Thursday informed media of stringent monitoring and control over its food sources, and the country has yet to be hit with any E.coli related cases. REUTERS/Ints Kalnins (LATVIA - Tags: ENVIRONMENT HEALTH SCI TECH)