GENEVA, April 25 (Reuters) - There is a "high risk of biological hazard" in Sudan's capital Khartoum after one of the warring parties seized a laboratory holding measles and cholera pathogens and other hazardous materials, the World Health Organization said on Tuesday. Speaking to reporters in Geneva via video link from Sudan, the WHO's representative in the country, Nima Saeed Abid, said technicians were unable to gain access to the National Public Health Laboratory to secure the materials. See here for a complete list of exchanges and delays