The Nobel Prize-winning agency Médecins Sans Frontières, also known as Doctors Without Borders, called on both international donors and the Zimbabwean government to do more.
"You've all heard about the disastrous cholera epidemic," said Dr. Christophe Fournier, MSF's international president, who spent four days touring Zimbabwe.
"However catastrophic this epidemic is, it is only the most visible manifestation of a much broader crisis in the whole country. Actually the whole public health system in Zimbabwe is down, it has collapsed."
World Health Organization figures released Monday indicate 77,650 people in Zimbabwe have been infected with cholera, a water-borne disease, since August.
So far, 3,688 people have died from the disease, which causes severe diarrhea.
The country also faces food shortages, malnutrition, collapsed infrastructure, political violence, displacement within Zimbabwe and to neighbouring countries, as well as an HIV epidemic, MSF said in the report released in Johannesburg, South Africa.
There was no immediate comment from the Zimbabwean government.
Malaria could be the next epidemic, the group said, because malaria season is approaching and people cannot afford to take preventive steps such as using insecticide-treated nets.
"The situation in Zimbabwe is causing inexcusable suffering," Fournier said.
"Urgent measures must be taken to ensure Zimbabweans have unimpeded access to the humanitarian assistance they so desperately need. The Zimbabwean government must guarantee that aid agencies can work wherever needs are identified and ease bureaucratic restrictions so projects can be properly staffed and drugs quickly procured."
This week, a unity government formed between ZANU-PF and the main opposition MDC, although Robert Mugabe remains the country's president.
Manuel Lopez, head of MSF's Zimbabwe operations, said Tuesday that he feared international donors would be reluctant to donate funds to a government headed by Mugabe.
Last year, Canada imposed sanctions against Zimbabwe including a ban on export of arms and freezing the assets of top officials, accusing the regime of human rights violations.
In the past, Mugabe's allies have accused western countries of trying to use the cholera outbreak as an excuse to oust him, and have blamed Zimbabwe's problems on western sanctions.
Zimbabwe has the world's highest inflation rate and faces acute shortages of most goods.