A little over a week after coronavirus quasi-emergency measures were lifted for 18 prefectures in Japan, there are already signs of a rebound in cases.

A panel of experts has voiced concern about a seventh wave of infections and stressed caution is needed.

The nationwide number of new infections in the 7 days through March 29th increased for the first time in almost a month and a half.

Chief Cabinet Secretary Matsuno Hirokazu said, "It is necessary to keep a close watch on the situation to see if this upward trend leads to a rebound."

One expert said one of the reasons for the rebound is the increase in infections among younger people due to gatherings during spring holidays and graduation ceremonies.

Professor Wada Koji of International University of Health and Welfare said, "The reason for the increase is that the Omicron variant is easily transmissible, and its sub-variant BA-2 is more likely to spread. If infections continues to rise, it will be necessary to take measures on the assumption that the sixth wave won't be the last."

The expert also stressed that vaccination can curb the rapid increase in infections and urged people to get booster shots as soon as possible.