COVID-19 infections have risen by a third in North America over the past week, due to surges in the United States and Canada, where new infections have doubled in the province of Alberta, the Pan American Health Organization (PAHO) said on Wednesday.

Hospitals in Alberta are facing critical staffing shortages, according to PAHO, the regional branch of the World Health Organization.

The United States is reporting more than 100,000 new daily infections for the first time since January and hospital capacity in many southern U.S. states remains worryingly low, the agency said.

As many parts of the world report a steady decrease in coronavrius infections, the Americas reported a nearly 20% increase in new cases, PAHO said.

Most South American countries are seeing continuing declines in COVID-19 cases and deaths, it said.

Infections are surging in Costa Rica, Guatemala and Belize and many hospitals there are saturated with COVID patients.

Meanwhile, infections have slowed in the Caribbean, with the exception of Grenada, Barbados and Bermuda that are reporting sharp jumps in new cases, and Jamaica saw its highest weekly case count since the beginning of the pandemic.

"We are encouraged that more than 30% of the people in Latin America and the Caribbean have been fully vaccinated against COVID-19," PAHO Director Carissa Etienne said in a weekly briefing.

But she said doses have not been equally distributed in the region and there is still a long way to go to reach everyone who needs a vaccine.

(Reporting by Anthony Boadle; editing by Emelia Sithole-Matarise)