Au-Prince, Haiti, Jan 20, 2010, SPA -- A powerful aftershock sent Haitians screaming into the streets today, collapsing buildings, cracking roads and adding to the trauma of a nation stunned by an apocalyptic quake eight days ago, according to AP. The magnitude-5.9 jolt matched the strongest of the aftershocks that have followed the huge quake of Jan. 12 that devastated Haiti's capital. The new temblor collapsed seven buildings in Petit-Goave, the seaside town closest to the epicenter, according to Mike Morton of the U.N. Disaster Assessment and Coordination agency, but there were no reports of people crushed or trapped, perhaps because the earlier quake frightened most people into sleeping outside. Wails of terror erupted in Port-au-Prince, where the aftershock briefly interrupted rescue efforts amid the broken concrete of collapsed buildings, and prompted doctors and patients to flee the University Hospital. Hundreds of thousands of Haitians remain homeless, hungry and in mourning _ most still waiting for the benefits of a nearly $1 billion global aid campaign that has brought hundreds of doctors and thousands of troops to the impoverished Caribbean nation. The U.S. Navy's floating hospital, USNS Comfort, dropped anchor in view of the capital on Wednesday with about 550 medical staff, joining teams from about 30 other countries trying to treat the injured. About 250,000 people were hurt in the quake and aid groups say many people have died for lack of medical care or adequate equipment. And the Pentagon announced that 2,000 more U.S. Marines would be sent to Haiti, adding 11,500 U.S. military personnel already on the ground or on ships offshore _ a number expected to reach 16,000 by week's end. At a golf course where U.S. troops have been trying to help 25,000 people living under sheets of plastic and old cloth, soldiers and quake victims alike raced for open ground as the quake began. A slow vibration intensified into side-to-side shaking that lasted about eight seconds. Some in Port-au-Prince said the far stronger Jan. 12 quake seemed to last for 30 seconds.