Health inspectors were ordered to close schools and markets, dig toilets and restrict people's movements in remote parts of three provinces, The National newspaper said, as the World Health Organization and Australia provided help.
The impoverished Pacific nation declared the emergency on Wednesday after the deaths doubled in a week. Earlier fears of a "mystery flu" proved unfounded after the virus was confirmed as seasonal influenza.
"Under this direction, all health professionals, government agencies and NGOs in this life-saving mission are empowered to improve hygiene and sanitation and contain the diseases in affected areas," Health Minister Sasa Zibe said.
Australia's foreign aid agency AusAID, quoting WHO figures, said 20 people had died from cholera, the country's first outbreak in decades, and 243 people had suspected cases.
The National said at least 51 people had died from flu, among more than 3,000 cases, and another 29 had been killed by dysentery. Health officials could not be reached to confirm the figures.
The country's WHO representative, Eigil Sorensen, said the situation was "concerning".
"It is concerning because of the general weakness of the health care system," Sorensen told AFP.
"It's like a litmus test to see how able they are to cope with such a situation. This is a big challenge."
AusAID said it had sent water purification tablets, protective clothing, water containers and rehydration salts, as well as an environmental health expert and logistical support.
PNG officials have warned the outbreaks were proving hard to control as they were in isolated areas, with the worst-hit Menyamya district some eight hours' rough drive from PNG's second city of Lae.
"This is the worst such crisis we have seen here," Morobe provincial health adviser Theo Likei said last week.