The Red Cross is appealing to donors, who have responded only reluctantly in the past, for more money to help keep the disease under control.
In a report, the International Federation of Red Cross and Red Crescent Societies said the outbreak of the waterborne disease has killed almost 4,300 people since August 2008.
"We stand now within days of 100,000 cases," said Red Cross spokesman Matthew Cochrane, adding that milestone had appeared unimaginable just a few months ago.
Cochrane said the outbreak 15 years ago killed 12,000 people in camps in what was then Zaire, as refugees fled turmoil following the genocide in Rwanda. What makes Zimbabwe's outbreak stand out, Cochrane said, was that it spread so quickly and was so deadly in a country at peace.
According to figures compiled by the U.N.'s World Health Organization, more than 98,000 cholera cases have been recorded in Zimbabwe since August.
Custodia Mandlhate, head of WHO's Zimbabwe operations, said in an e-mail that the outbreak appeared under control, but added that "our main challenge is now to make sure that preparedness for future epidemics is done."
Cholera is usually easily treated. The scale of Zimbabwe's outbreak is blamed on the collapse of the country's water and health infrastructure following years of violent political impasse.
Donors have been slow to provide funds to rebuild that infrastructure because they do not trust President Robert Mugabe, accused of trampling on democracy and ruining a once-thriving economy. Mugabe joined his longtime rivals in a unity government in February, but has been slow to act on his promises of reform.
The global financial crisis also has slowed aid and development giving.
Late last year, the Red Cross asked the international community for about $9 million for an emergency response in Zimbabwe that included distributing water purification chemicals and ensuring tent hospitals had drugs and trained staff. The Red Cross had to end that operation early when it received only 45 percent of the funds it needed.
Now, the Red Cross is asking for $3.44 million for the next stage, rehabilitating water systems, digging wells and constructing latrines. The agency, conscious of the international community's reluctance to fund development work while Mugabe continues to stall reforms, stressed that donations are necessary to complete humanitarian work.
Taking steps now to prevent a cholera resurgence, Cochrane said, would ensure aid workers are not coming to donors again in a year asking for millions in emergency funding. "Cholera has retreated, but it hasn't been defeated," he said.