A Dengue fever outbreak ravaging the island nation of Nauru has now hit about 10 per cent of asylum seekers living at the Australian-run regional processing centre.

The Department of Immigration and Border Protection confirmed 41 people living at the facility had contracted the mosquito-borne viral disease by the end of March.

That number is likely to have risen as health authorities struggle to contain an outbreak that is estimated to have affected up to 900 people on the island of 10,000.

But authorities, including Australia's immigration department, are refusing to detail the extent of the crisis or what strategies have been put in place to combat it.