Yaravirus, named after the mermaid Yara, was discovered in Lake Pampulha in Belo Horizonte last month. According to Brazilian mythology, she would lure men to live underwater with her.
Scientists have been left baffled as Yaravirus does not appear to be related to any other virus in the world.
Around 90 percent of its genes have never been seen before.
It is described as a “new lineage of amoebal virus with a puzzling origin and phylogeny”.
In a bioRxiv report, scientists said: “Using the standard protocols, our first analysis was not able to find any recognisable sequence of the typical viral genes in Yaravirus.
“In fact, following the current protocols, Yaravirus would not even have been recognised as a virus.
“This expands our knowledge of the diversity in the DNA of viruses.
“The distance between Yaravirus and the rest of the viruses shows that we are still in the early stages of virus genomic diversity.”
The mysterious virus is not believed to pose a threat to humans.
In the UK, a total of 1,358 people have been tested.
Of these, 1,350 were confirmed negative and eight positive.
A healthcare worker at Worthing Hospital and a locum doctor working in Brighton are among the eight cases.
And two prisoners at HMP Bullingdon in Oxfordshire are being tested and held in isolation.
One of the men is understood to have recently transferred from a Thai jail.
Speaking in Birmingham yesterday, Boris Johnson praised the response of the NHS and said anyone concerned about the virus should “simply follow their advice”.
The Prime Minister said: “We are a great country, we have got a fantastic NHS, we have got fantastic doctors and advice, and they should simply take the advice of the NHS.
“People have every reason to be confident and calm about all that kind of thing… all the coronavirus, and any threats from disease.”
Additional reporting by Maria Ortega.