WASHINGTON, Jan 8 (Reuters) - Dengue fever -- a tropical infection that usually causes flu-like illness -- may be poised to spread across the United States and urgent study is needed, health officials said on Tuesday.

Cases of the sometimes deadly mosquito-borne disease have been reported in Texas and this may be the beginning of a new trend, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and his senior scientific adviser, Dr. David Morens.

A warming climate and less-than-stellar efforts to control mosquitoes could accelerate its spread northwards, they cautioned.

"Widespread appearance of dengue in the continental United States is a real possibility," they wrote in a commentary in the Journal of the American Medical Association.

"Worldwide, dengue is among the most important reemerging infectious diseases, with an estimated 50 to 100 million annual cases, 500,000 hospitalizations and, by World Health Organization estimates, 22,000 deaths, mostly in children."

They compared dengue to West Nile virus, which first appeared in New York in 1999 and has now spread to the entire continental United States, Canada and Mexico. West Nile killed at least 98 people in the United States last year.

Both viruses are carried by mosquitoes. Dengue can be carried by the Aedes albopictus or Asian tiger mosquito -- first seen in 1985 in the United States -- as well as the more common Aedes aegypti species.

Most people infected with a dengue virus have no symptoms or a mild fever. It can cause minor bleeding from the nose or gums, but can also cause severe fever and shock and without treatment can kill.

"The combined effects of global urbanization and increasing air travel are expected to make dengue a growing international health problem for the foreseeable future," Fauci and Morens wrote. (Reporting by Maggie Fox; editing by Julie Steenhuysen and Todd Eastham)

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