BEIJING (AP) — World health officials expressed "great concern" Wednesday that a dangerous new virus is starting to spread between people outside of China, a troubling development as China and the world frantically work to contain the outbreak. For a second day, the number of infections grew dramatically.

The new virus has now infected more people in China than were sickened there during the 2002-2003 SARS outbreak. On Wednesday, the number of cases jumped to 5,974, surpassing the 5,327 people diagnosed with SARS.

The death toll, which rose to 170 on Wednesday, is still less than half the numb...