Border guards at Brussels Airport have caught 820 using forged test certificates in the last few months and the vast majority accept an immediate 750€ fine to escape further prosecution.
The variant's global spread suggests it could have a major impact on the COVID-19 pandemic, and the time to contain it is now before more Omicron patients are hospitalised, WHO director-general Tedros Adhanom Ghebreyesus said.
WHO chief scientist Soumya Swaminathan said that the variant was successfully evading some immune responses, meaning that the booster programmes being rolled out in many countries ought to be targeted towards people with weaker immune systems.
Omicron appears to be better at evading antibodies generated by some COVID-19 vaccines but there are other forms of immunity that may prevent infection and disease, WHO officials said.
At least 115,000 nurses have died from COVID-19, but Catton said this World Health Organisation figure from the start of the pandemic through May was conservative and the true figure is probably twice that.
Senior health official Vinod Kumar Paul told a news briefing that government experts were studying data on boosters but "our emphatic view...is to (first) cover every adult with (just) the primary two doses." The government has said this target can be achieved by January.
PM Rutte says the government's new order builds on an existing partial lockdown already in force that requires bars, restaurants and other public gathering places such as cinemas and theaters to close at 5pm.
WHO noted that Omicron is spreading rapidly even in countries with high vaccination rates or where a significant proportion of the population has recovered from COVID-1levels of population immunity
Brazil, with more than 1.1 million cases and 51,000 deaths, has been affected more than anywhere but the US, which has reported more than 2.3 million cases and 120,000 deaths, according to a tally kept by Johns Hopkins University.
Seven other countries risked less extreme but "potentially dangerous" warm weather: Belgium, Estonia, Finland, Latvia, the Netherlands, Portugal and Sweden, it said.