The NGO, Medecins Sans Frontieres, is encouraging people with suspected cholera symptoms in Morobe Province in Papua New Guinea to seek the free treatment being offered.
The province has been hit by simultaneous outbreaks of shigella, influenza and cholera.
There have been no reported deaths in the past two weeks but thousands are still suffering the effects.
Medicins Sans Frontieres is offering free treatment for suspected cholera sufferers at a number of sites.
Its emergency co-ordinator, Steven Cooper, says although highly contagious, cholera is preventable and is treated easily.
He says many patients can be treated if they get the correct amount of electrolytes to rehydrate.
Mr Cooper says more severe cases are treated using an intravenous drip and can feel better within 24 hours.