Two patients in Brazil have tested positive for more than one strain of coronavirus at the same time.

Believed to be the world’s first case of double infection, researchers at Feevale University found out after taking swabs from 90 infected people in Rio Grande do Sul, southern Brazil. 

They posted their findings on a medical website, MedRxiv, though this study has not been reviewed by the scientific community. 

“These co-infections can generate combinations and generate new variants even more quickly than has been happening,” said the lead researcher, Fernando Spilki, a virologist at Feevale University told Reuters. 

Mr. Spilki added that the discovery raised concerns about the viral load currently circulating in Brazil as co-infection can only occur due to high transmission numbers of the different strains.  

Both patients, in their 30s, were infected in November with the P.2 variant of the virus but tested positive for the second variant of the virus.

They did not need to be hospitalised. However, the infections manifested in symptoms such as a dry cough, coughing, sore throat, and headache in the second. 

P.1, the vaccine-resistant strain, has led to travel bans placed on South American countries.

In January, the United Kingdom placed a travel ban on people who had travelled from, or through Argentina, Brazil, Bolivia, Chile, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay, and Venezuela.

The United States’ President Joseph Biden also placed travel bans on Brazil due to concerns about the spread of the vaccine-resistant variants.