RIO DE JANEIRO: Brazil faces a new wave of COVID cases just as the soccer-crazed nation is gathering en masse to follow the World Cup, with new coronavirus sub-variants and delayed vaccine boosters raising alarms among public health specialists.

On World Cup game days, many Brazilians get time off work to pack into bars and restaurants or gather for home barbecues to watch the games, rooting for a national team seeking its sixth world champion title in Qatar.

New COVID cases in Brazil jumped last week by 230% from early November to a level not seen since August, according to official figures. Related deaths jumped to 116 on Tuesday from single digits in October.

"At every gathering there is a high possibility of transmission, because it's very easy to catch", said Margareth Dalcolmo at the Oswaldo Cruz Foundation, a biomedical research center in Rio de Janeiro.

Brazilian health regulator ANVISA announced late on Tuesday that face masks would be required again in airports and on all flights to prevent the spread of the virus.

It also decided on Tuesday to approve the use of two new vaccines made by Pfizer Inc that protect against the Omicron sub-variants BA.1 and BA.4/BA.5 as well as the original virus, to be used as boosters.

Experts say the delay in rolling out vaccines to tackle highly infectious new variants added to the surge in contagions.

Almost 690,000 Brazilians have died from COVID, the world's second-highest official death toll behind the United States.

New infections in Brazil are mainly caused by the BQ.1 strain of the Omicron sub-variant BA.5 strain, causing milder symptoms in people who have been fully vaccinated. That is likely to translate to fewer deaths than prior waves, although hospitals are receiving a growing number of patients, health officials said.

With Brazil making its debut in Qatar on Thursday, experts recommended that fans wear masks if they are indoors, and take all necessary hygiene precautions to avoid contagion.