HARARE (Reuters) Cholera has killed more than 3,000 Zimbabweans and infected at least 57,000, the World Health Organization said on Wednesday, making it the deadliest outbreak in Africa in 15 years. The disease has spread as rival political parties struggle to implement a power-sharing agreement reached in September and seen as a chance to ease the humanitarian crisis and save the faltering economy. Regional leaders decided at a summit on Tuesday that a unity government should be formed next month. Fears of the cholera spreading in Zimbabwe have stepped up pressure on rival parties to end the political uncertainty. WHO figures showed an increase of 57 deaths and 1,579 new infections since Tuesday. The outbreak has hit the entire country, leading to a high overall case fatality rate of 5.3 percent. Opposition leader Morgan Tsvangirai has said he agrees to form a government with President Robert Mugabe although his Movement for Democratic Change voiced disappointment with the deal reached at the summit, a South African newspaper reported. MDC officials are expected to meet on Friday to discuss how to proceed.