Genetic testing has shown that the recent outbreak of haemorrhagic fever in South Africa was caused by a new strain of arenavirus, not previously seen. The news was given by Dr Ian Lipkin of Columbia University, New York. Experts are puzzled as to why the new strain is so pathogenic. It is apparently not like Lassa fever - caused by a related virus.
Samples from patients were sent to the Centres for Disease Control and Prevention and to Lipkin's laboratory in New York.
