ICN chief executive Howard Catton told a virtual briefing that infection rates, medication errors and mortality rates "are all higher where there are too few nurses".
Furthermore, "shortages exhaust our current nursing workforce", he added.
In fighting the pandemic, Mary Watkins, who co-chaired the report for Nursing Now, called for urgent investment in virus tests for healthcare workers.
"We have a very high proportion of healthcare workers not going to work because they're afraid that they've been infected and that they can't prove that they have not got the infection -- or that they've had it, and they're over it," she said.
Catton said that 23 nurses had died in Italy and cited figures suggesting that around 100 health workers had died around the world.
Meanwhile, he said there were reports of nine per cent of health workers being infected in Italy and "we're now hearing of rates of infections up to 14 percent in Spain".
He also cited reports of "completely unacceptable and reprehensible" attacks on health workers battling Covid-19, largely due to ignorance about their work, combined with countries not doing enough to protect them.
"Covid-19 is putting it into a very stark lens for us all," he said, though he welcomed the growing appreciation in some countries of nurse's work.
Catton said that could help change perceptions of the value of nursing -- which in turn might help make it a more attractive profession.
Beyond Covid-19, Watkins said many wealthier countries were not producing enough nurses to meet their own healthcare needs, and were therefore reliant on migration, exacerbating shortages in poorer countries.
"Eighty per cent of the world's nurses only currently serve 50 per cent of the world's population," she noted.
Catton warned of risks that richer countries would rely on the Philippines and India to "supply the world with nurses", which could lead to significant shortages in India.
The experts said nursing remains female-dominated and needed to recruit more men.
"There is clear evidence that where there are more men in any profession in the world, the pay and the terms and conditions improve," Watkins said.