The coronavirus variant first found in Brazil may spread more easily or reinfect people who've already had the virus, researchers say. 10 cases have been confirmed in the US.

• The coronavirus variant first found in Brazil may reinfect people who've already had the virus, scientists said.
• The variant could also be between 1.4 and 2.2 times more transmissible than other variants, they said.
• The P.1 variant has been found in 28 countries, including 10 cases across five US states.

The coronavirus variant first found in Brazil may be more transmissible or may reinfect people who've already had the virus, scientists said in a report.

The variant has already spread to almost 30 countries.

The variant, known as P.1, could be between 1.4 and 2.2 times more transmissible than other variants, researchers from the University of São Paulo, Imperial College London, and the University of Oxford said.

Their research in the Brazilian city of Manaus suggested that the variant also evaded between 25% and 61% of the protective immunity that people get after being infected by other SARS-CoV-2 strains.

The P.1 variant led to a steep rise in cases in Manaus in the state Amazonas, where blood-test results had already shown high rates of population immunity, the scientists said. This "may point to risk of re-infection or increased transmissibility," they wrote.

"The exact trade-off between increased transmissibility and evading immunity is not currently known," the researchers added.

P.1 was first detected in Manaus on December 4.

But the researchers said the variant had likely been circulating in the region since early November and caused a second wave of coronavirus infections in Manaus between December and January. By January 21, 91% of people with COVID-19 in the region were infected with the P.1 variant, the World Health Organization said.

The variant has spread beyond Brazil and is now present in 28 countries, including the UK, Italy, and Belgium, the WHO reported. There have been 10 reported cases of P.1 across five states in the US after the first known case was reported in Minnesota on January 26, the CDC said.

The new study, which has not yet been peer-reviewed, only looked into acquired immunity and not vaccine effectiveness. The WHO said that the impact of the variant on vaccines is "under investigation."

The WHO also said that scientists are investigating whether or not P.1. is more deadly. The new study found that P.1 is associated with an increase in the risk of mortality of between 10% and 80% compared to previously circulating variants in Manaus, but it noted that the city's health system "collapsed" during the second wave.

"We therefore cannot determine whether the estimated increase in relative mortality risk is due to P.1 infection, stresses on the Manaus healthcare system, or both," the researchers wrote.

P.1 isn't the only variant scientists are looking into. Experts are also studying the B.1.1.7 variant, first identified in the UK, and the 501.Y.V2 variant, first found in South Africa. Scientists think these may both be more contagious that the original strain.