Worried health officials say that 95 percent of the cases are in one small village in Morobe Province on the northwest coast of the Pacific nation, but warned the illnesses were proving difficult to control.
Twenty-seven villagers in Morobe's Menyamya district have died from an influenza-like illness since August 3, while a further 20 were felled by dysentery, provincial health adviser Doctor Theo Likei told AFP.
"Roughly 2,000 people are sick in about 12 villages and we suspect influenza and dysentery are the cause," he said. "So far there have been about 47 deaths, about 90 percent of them in the village of Akwanda.
"The problem is that once it gets started in remote areas it's very hard to stop and the area is hard to reach, but we are hoping the illness will remain isolated to pockets of the area so we can manage it," he added.
It was not immediately known whether the flu-like illness was swine flu or another strain. The World Health Organization has taken samples from stricken villages and is expected to report back within two weeks, Likei said.
"This is the worst such crisis we have seen here, Likei said. "The situation is not that encouraging as of today but we will monitor closely over the next two days or so and hope it comes under control."
Four three-man health teams are on the ground treating victims of the outbreaks and encouraging villagers to restrict their movements, boil water and take care when preparing food to avoid spreading the disease further.
Doctors do not believe the eruption of two diseases about 120 kilometers (75 miles) west of PNG's second city of Lae are linked as dysentery is usually bacterial and flu is viral.
But complicating the medical relief effort, a separate eruption of cholera in the east of Morobe province has killed a further seven adults and sickened 73 other people, Likei said.
"We have yet to take the necessary action to make sure the situation is under control. I hope to get teams in there by chopper soon," he said.