- Associated Press - Thursday, February 10, 2011

SAO PAULO (AP) - Dengue cases have risen sharply in at least one key Brazil state, officials said Thursday, building on a steady increase over the past year nationwide.

The number of dengue cases in Rio de Janeiro state rose to 3,582 cases in January, more than double the 1,447 registered in January 2010, which itself was the start of a year that saw dengue cases triple across Brazil.

Alexandre Chieppe, head of Rio state’s epidemiological service, said by telephone that the increase is mostly due to the resurgence of the Type 1 dengue strain that had largely been absent in the state. As result, residents have not been able to develop immunity to it as they have for Types 2 and 3, which have been the most common.

He said that exposure to a single strain of the disease helps create immunity to that particular variant, but subsequent infection by a different strain can cause the sometimes fatal hemorrhagic dengue.

Preliminary figures provided by the national Health Ministry show that the number of dengue cases nationwide rose from 324,000 in 2009 to nearly one million in 2010.

A ministry spokeswoman also attributed that rise to the reappearance of Type 1 dengue after an absence of at least 15 years. She asked not to be identified in line with departmental regulations.

Chieppe said that the Rio numbers do not indicate an epidemic in the making, “but we are on the alert because dengue hits its peak in March and April.”

“This is the time of year when health services must intensify preventive measures and work harder to detect people with the symptoms of the disease like high fever, headaches, and severe muscle and joint pain,” he said. “It is the time of year when everyone, rich or poor, must be aware that they can come down with dengue.”

He said one of the measures adopted combat the mosquitoes that spread the disease is the weekly fumigation of the Sambodromo stadium that next month will host Rio’s famed carnival parade.