TOKYO, July 15 (Reuters) - Japanese stocks sank on Thursday, dragged by caution ahead of corporate earnings season and a surge in COVID-19 cases a week before the Tokyo Olympics get underway. The Nikkei share average dropped 0.9% to 28,343.83 by the midday break, with the broader Topix sliding about the same margin to 1,946.37. Tokyo reported 1,149 new infections on Wednesday, the most since mid-January, despite a new state of emergency that began on Monday and runs through Aug. 22. Many worry that the influx of foreign athletes and Olympic officials could also trigger another surge in cases. “Infections are still going up, and the Olympics is just about to start, which is making investors cautious,” said Masahiro Ichikawa, chief market strategist at Sumitomo Mitsui DS Asset Management. “Earnings season is also just about to start, so there are some position adjustments taking place,” he said, adding that it is also contributing to the weakness in equities. Uniqlo clothing brand owner Fast Retailing Co. slipped 1.3% before announcing financial results later on Thursday. On the Nikkei, Nikon Corp. was the biggest loser, tumbling 5.4%. Hitachi extended its drop from a two-decade high to a second day, sliding 3%. Among Topix sectors, mining lost the most, falling 2.3% amid a slide in crude oil prices. [O/R} Carmakers weakened 1.1% after the European Union announced tighter emissions restrictions that will make it impossible to sell gasoline and diesel cars by 2035, including hybrids. Isuzu Motors fell the most, losing 2.7%, followed by a 2.6% slide for Toyota-owned truck maker Hino Motors . Nissan Motor Co. sank 1.9%. Toyota Motor Corp fared better, falling 0.6%. Editing by Uttaresh.V Our Standards: The Thomson Reuters Trust Principles.