A total of 44,818 new COVID-19 cases were confirmed between November 2 and 29, a four-fold increase from October and a 25-fold increase from September, it said.

The results of epidemiological investigations show that a significant proportion of last month's cases were linked to infections in families and at work, as well as in treatment and supportive care facilities.

Some 4,520 cases, or more than 10 percent of all confirmed cases, were not investigated in November. Of these, 4,036 cases could not be investigated because the NPHC did not have the contact details of the infected people and could not reach them.

More than a third of those who tested positive in November said they did not know how they had contracted the virus.

In a worrying trend, the percentage of cases that could not be traced to any known sources jumped to 38 percent in November, from 25 percent in October, 20 percent in September, 19 percent in August, and 18 percent in July, the center said.

This means an increased risk of exposure to COVID-19 everywhere where there is contact between people, especially indoors, it warned.