A record 9.5 million new COVID-19 cases were reported around the world during the week December 27-January 2, the World Health Organisation said on Thursday, with its chief warning that the "tsunami of cases" caused by the new Omicron variant was overwhelming health systems around the world.

The COVID-19 Weekly Epidemiological Update, released by the global health agency Thursday, said that during the week December 27, 2021 to January 2, 2022, following a gradual increase since October, the global number of new cases increased sharply by 71 per cent as compared to the previous week.

The number of new deaths decreased by 10 per cent. This corresponds to just under 9.5 million new cases and over 41,000 new deaths reported during the last week. As of January 2, a total of nearly 289 million cases and over 5.4 million deaths have been reported globally, the update said.

"Last week, the highest number of COVID-19 cases were reported so far in the pandemic. And we know, for certain, that this is an underestimate of cases because reported numbers do not reflect the backlog of testing around the holidays, the number of positive self-tests not registered, and burdened surveillance systems that miss cases around the word," WHO Director-General Tedros Adhanom Ghebreyesus said.

Addressing a press briefing in Geneva, he cautioned that while the Omicron variant appears to be less severe compared to Delta, especially in those vaccinated, it does not mean it should be categorised as 'mild'.

"Just like previous variants; Omicron is hospitalising people and it is killing people. In fact, the tsunami of cases is so huge and quick, that it is overwhelming health systems around the world," he said.

The WHO update said that all regions reported an increase in the incidence of weekly cases, with the Region of the Americas reporting the largest increase (100 per cent), followed by the South-East Asia (78 per cent), European (65 per cent), Eastern Mediterranean (40 per cent), Western Pacific (38 per cent) and the African (7 per cent) Regions.

The European Region continued to report the highest incidence of weekly cases (577.7 new cases per 100,000 population), followed by the Region of the Americas (319.0 new cases per 100,000 population). Both regions also reported the highest weekly incidence in deaths.

The African Region was the only region to report a weekly increase in the number of new deaths (22 per cent). All other regions reported a decrease in the incidence of deaths, including the Americas (18 per cent), Western Pacific (10 per cent), South-East Asia (9 per cent), Eastern Mediterranean (7 per cent) and the European (6 per cent) Regions.

The highest numbers of new cases were reported from the United States of America (2,556,690 new cases; 92 per cent increase), the United Kingdom (1,104,316 new cases; 51 per cent increase), France (1,093,162 new cases; 117 per cent increase); Spain (649,832 new cases; 60 per cent increase) and Italy (644,508 new cases; 150 per cent increase).

The update noted that after a declining trend in the number of weekly cases since the end of July 2021, the South-East Asia Region reported an increase in case incidence of 78 per cent, corresponding to over 135,000 new cases.

However, the number of new weekly deaths decreased by 9 per cent, with over 2400 new deaths reported. Half of the countries (5/10) reported weekly increases in the number of new cases of over 10 per cent.

After India, the highest increases in new cases were reported by Bangladesh (48 per cent increase) and the Maldives (31 per cent increase). The highest numbers of new cases were reported from India (102,330 new cases; a 120 per cent increase), Thailand (19,588 new cases; a 6 per cent increase) and Sri Lanka (4286 new cases; an 8 per cent increase).

The highest numbers of new deaths continued to be reported from India (2088 new deaths; an 8 per cent decrease), Thailand (140 new deaths; a 31 per cent decrease), and Sri Lanka (135 new deaths; similar to the previous week).

Ghebreyesus noted that first-generation vaccines may not stop all infections and transmission but they remain highly effective in reducing hospitalisation and death from this virus.

"So as well as vaccination, public health social measures, including the wearing of well fitting masks, distancing, avoiding crowds and improving and investing in ventilation are important for limiting transmission," he said.

He lamented that at the current pace of vaccine rollout, 109 countries would miss out on fully vaccinating 70 per cent of their populations by the start of July 2022.

"The essence of the disparity is that some countries are moving toward vaccinating citizens a fourth time, while others haven't even had enough regular supply to vaccinate their health workers and those at most risk," he said.