The country's four main hospitals, in the capital, Harare, and the western city of Bulawayo, were "virtually closed", while smaller district hospitals and municipal clinics "are barely functioning or closed", the Zimbabwe Association of Doctors for Human Rights (ZADHR) said.
"Sick people in need of attention are being turned away."
Harare's two big state hospitals have withdrawn maternity services, meaning that women needing to deliver by Caesarean section "will needlessly die in childbirth", the doctors' association said.
Zimbabwe's only medical school closed on Monday "because it became impossible to teach in non-functioning health institutions". A cholera epidemic that broke out early last month caused "hundreds of preventable deaths" and spread to at least five of the country's 10 provinces, ZADHR said.
"Ad hoc measures" by President Robert Mugabe's government had done nothing to deal with the breakdown of water supplies to urban areas where residents were "surrounded by flowing raw sewage".
The state-owned Chronicle newspaper in Bulawayo reported on Wednesday that the death toll in the crowded southern border town of Beitbridge had risen to 44 since the cholera outbreak was discovered there last Friday night.
Officials at the Beitbridge hospital were appealing to relatives to collect the bodies of the dead, because the hospital mortuary can take only six bodies.
"The government should declare the cholera outbreak a national disaster and solicit international support to bring it under control and restore the supply of safe water and sanitation systems to Zimbabwe's population," ZADHR said.
On Tuesday a demonstration by state doctors and nurses over the government's failure to prevent the collapse of the health system was broken up by baton-wielding riot police.
Medical officials requesting anonymity say the government has been covering up the severity of the cholera outbreak and has stopped issuing information on the spread of the epidemic in some parts of the country.
The state of the country's health sector is symptomatic of a wider economic collapse under 84-year-old Mugabe.
Mugabe, who has ruled Zimbabwe for 28 years, is on the brink of forming a government over the heads of the Movement for Democratic Change (MDC), with whom he had previously agreed to share power.
MDC leader Morgan Tsvangirai has declared he will not participate in the agreement unless Mugabe shares power equally.
Last week state media reported that a draft bill, needed to put the proposed power-sharing government into effect, had been completed.
The state-controlled daily Herald newspaper quoted Minister of Information and Publicity Sikhanyiso Ndlovu as saying the draft had been sent for scrutiny to former South African president Thabo Mbeki, the mediator in Zimbabwe's talks.
After a 30-day period for public scrutiny, "the president shall appoint a Cabinet", the minister said. - Sapa-dpa