Gustav barged ashore as a hurricane in Haiti on Tuesday and its driving rains took at least 59 lives there and eight in the neighboring Dominican Republic on the island of Hispaniola.
Officials said the deaths were due mostly to flooding and mudslides in western and southern Haiti.
In Jamaica, shops, post offices and schools shut their doors and authorities ordered nonessential workers to stay home before Gustav made landfall on Thursday afternoon. The storm buffeted the lush, mountainous island with high winds and torrential rains that soaked some sugar cane fields.
Rooftops flew off houses in isolated areas and a 50-year-old man fell to his death after a strong gust of wind blew him out of the tree where he was picking breadfruit as the storm closed in on Jamaica's central Manchester parish.
Gustav is the first serious Atlantic storm since the 2005 hurricane season to threaten New Orleans and the 4,000 US energy platforms in the Gulf.
Katrina and Rita destroyed 124 platforms and severed pipelines when they swept through the Gulf of Mexico as Category 5 storms on the five-step Saffir-Simpson scale of hurricane intensity. Katrina came ashore near New Orleans on August 29, 2005, as a Category 3 hurricane and flooded the city. It killed 1,500 people along the Gulf Coast and caused US$80 billion in damage.
US Army Corps of Engineers program manager Bill Irwin told a news conference on Thursday that gaps remained in New Orleans' flood control system and that it was still vulnerable despite improvements after Katrina.
The agency was rushing to install temporary flood-prevention structures, Irwin said.
Energy companies shut down production and pulled workers from Gulf offshore rigs. The Louisiana Offshore Oil Port, the nation's only deepwater oil port, which normally offloads about 1 million barrels of foreign crude per day, expected to stop working over the weekend.
On its current path, Gustav will threaten the Cayman Islands and western Cuba before entering the Gulf.
Energy traders also warily watched newborn Hanna, 260 miles northeast of the northern Leeward Islands. The storm was moving west-northwest and could become a hurricane by next week.