With authorities around the world battling to halt the spread of novel coronavirus pneumonia, more countries have confirmed new cases.

A Brazilian government test has confirmed the first case in Latin America, a source said on Wednesday, after a Sao Paulo hospital flagged the possible infection of a 61-year-old who had visited Italy, according to Reuters.

The virus has spread to Switzerland, Austria, Croatia and Greece, which reported their first confirmed cases. Germany, France and Spain, which had previously reported cases, confirmed new infections in people who were from or had visited northern Italy.

Matshidiso Moeti, the World Health Organization's regional director for Africa, tweeted on Wednesday that Algeria announced the first confirmed case of COVID-19. "The window of opportunity the continent has had to prepare for#coronavirus disease is closing. All countries must ramp up their preparedness activities," she said.

On Tuesday, the United States Centers for Disease Control and Prevention warned that the virus could bring "severe" disruption to the US, telling Americans to begin preparing for the coronavirus to spread within the country.

"It's not a question of if. It's a question of when and how many people will be infected," said Anne Schuchat, the CDC's principal deputy director.

San Francisco Mayor London Breed declared a state of emergency on Tuesday over coronavirus concerns, although the city has seen no confirmed cases. "The global picture is changing rapidly, and we need to step up preparedness," she said in a statement.

The CDC said the number of novel coronavirus cases in the US has jumped to 57, including 40 American passengers from the cruise ship Diamond Princess, which was quarantined in Yokohama, Japan, due to a coronavirus outbreak on board.