It started in mid-April with a fever, as if her body were trying to burn itself up. Then 39-year-old Belkys Jimenez developed a pounding headache and pain in her muscles and joints. Her feet and ankles ballooned, and even taking a step became difficult. Jimenez had dealt with hypertension for years, but this was something new.

Over the next two weeks, her symptoms came and went. Several times, she visited a doctor in her hometown of Bajos de Haina, in the Dominican Republic. He provided acetaminophen for the pain and swelling and promptly dismissed her. The night of April 30, a Wednesday, Jimenez was feeling better. Before going to bed, she told her mother she would wake up early to go to the market.

But the following morning, Jimenez didn't get out of bed. Her worried mother found her daughter cold to the touch, without a pulse. "One day she was fine; the next day she was bad," Jimenez's mother told the Dominican television network Tele Noticias. "She never got better from this."

Jimenez's hypertension had combined with a new, debilitating illness, and the complications had killed her, her mother said. The sudden death shook her neighborhood, but the rapid onset and severity of her illness surprised no one. Hundreds of residents of Bajos de Haina, a gritty industrial town just south of Santo Domingo, were suffering from the same symptoms. They had fevers as high as 104, migraine-like headaches and sometimes bright-red rashes covering their limbs. But the worst was the joint pain -- typically so severe it made ordinary tasks like twisting doorknobs and tying shoelaces unbearable and forced even healthy young men to walk as if they had aged 50 years overnight.

"This is like a plague that the Bible talks about," one elderly woman said after Jimenez's death.

The cause was a mosquito-borne virus that, just months earlier, almost no one in the town knew about: chikungunya. There is no cure or antidote, and, while typically not fatal, the disease can leave victims in agonizing pain for months or years. In parts of Africa and Asia, it has been around for decades, but in the Dominican Republic -- and the rest of the Americas -- it was brand-new. Though travelers had been diagnosed before, never had anyone in the Western Hemisphere contracted the disease from local mosquitoes until last December 6, when the Pan American Health Organization confirmed two cases on the tiny Caribbean island of Saint Martin.

The region soon faced a pandemic. By mid-summer, when the world's attention was suddenly consumed by another African viral epidemic -- ebola -- chikungunya had infected hundreds of thousands in the Caribbean and was gradually creeping into the United States. People from Maine to Texas to California contracted it after traveling to affected countries, and this past July 17, public health officials announced that two Florida residents had been infected by local mosquitoes -- marking the first time chikungunya had been acquired in the United States. That left the door open to thousands of new American cases.

"It's a new disease," says Dr. Scott Weaver, a virologist at the University of Texas Medical Branch. "I think it's one of the most serious threats from a mosquito-borne disease in the U.S. in many years."