BRUSSELS (REUTERS) - The European Union is warning governments not to reduce the 14-day quarantine for people infected with Covid-19 as some develop the infection even after two weeks, the head of the bloc's health agency said, signalling a new surge in cases in Europe.

Germany, the EU's largest country, informed EU authorities that it planned to shorten the quarantine length, following similar moves by the Netherlands and Norway, according to minutes of a late-August meeting.

"We are looking to provide some evidence to decision makers on what kind of risks they would take if quarantine was shorter," Dr Andrea Ammon, head of the European Centre for Disease Prevention and Control, told EU lawmakers in a regular hearing on Wednesday (Sept 2).

She cautioned that in 3-4 per cent of cases, infections emerge only after 14 days, which is currently the standard length of the Covid-19 quarantine.

Last week, Germany decided that from October, people returning from high-risk regions abroad will have to quarantine for five days.

The partial loosening of Covid-19 preventive measures comes as Europe is experiencing a new increase in cases.

"The virus has not been sleeping over the summer. It did not take vacation," Dr Ammon told lawmakers.

She said this week's data showed that across Europe, there were 46 cases per 100,000 people.

"We are almost back to numbers that we have seen in March", Dr Ammon said, referring to the beginning of the peak phase in Europe.

Infections in March in Europe began growing steadily to about 40 per 100,000 people at the end of the month, according to data from the European Centre for Disease Prevention and Control, and kept increasing to around 70 per 100,000 by the end of April.

The current increase in cases was due in part to more testing.

New cases also concern largely younger people, she said, a new pattern that had resulted in stable hospitalisation numbers, as the illness is more serious for older people who were hit hard in March and April.

However, Dr Ammon said hospitalisations were now growing again, signalling spikes in cases also among the elderly.

The data, which concern the 27 EU countries, Britain, Norway, Iceland and Liechtenstein, varied greatly between states from two to 176 per 100,000 people, Dr Ammon said without citing specific countries.