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WASHINGTON (Reuters) - Tourists traveling by plane and the growth of cities are combining to help new and old infections spread around the world, experts said on Monday.
Viruses such as Chikungunya and dengue fever are finding new homes or returning to places where they were eradicated, the researchers told an infectious diseases meeting.
And new methods of diagnosing infections have led to the discovery of dozens of viruses causing often-serious disease.
"As urbanization spread, so did the mosquito," Duane Gubler of the University of Hawaii told a news conference at a joint meeting of the American Society of Microbiology and the Infectious Diseases Society of America.
Researchers at the Pan American Health Organization told the meeting that dengue fever, which can cause mild illness or deadly hemorrhagic disease, has come back after decades of eradication successes in Latin America.
They said 1.03 million cases of dengue were reported in the 1980s and 2.7 million in the 1990s, but 4.6 million were reported from 2000 to 2007.
The "re-emergence of epidemic dengue is closely associated with global urbanization and global transportation," Gubler said. "Pathogens of all kinds -- many of them actually move in infected people but they also move in infected animals and mosquitoes."
New infections are a threat, as well.
Dr. Ian Lipkin of Columbia University in New York said his lab, using new genetic sequencing techniques, has identified 75 new pathogens -- including a new rhinovirus that has caused serious disease in "scores of children" around the world.
Rhinoviruses are spread person-to-person only and usually cause common colds but this version appears more like severe influenza, Lipkin told the news conference.
"It was literally under our noses and in our noses for a long time," Lipkin said. "It has been found in Asia, Africa, Oceania, North America and Europe," he added. "It clearly is an important pathogen."
Chikungunya virus, which causes painful and sometimes crippling or deadly symptoms, has spread to several new countries in the past two years. One traveler brought it to Italy last year, Gubler noted.
"The same virus was introduced into India and into Sri Lanka, most likely via infected travelers," Gubler said.
Outbreaks of Chikungunya, which originated in Tanzania in 1952 but did not spread much outside of Africa until 2005, have been helped by mutations that let it travel via the Asian tiger mosquito, Aedes albopictus.
In 2005 on tiny Reunion Island in the Indian Ocean, it infected more than a third of the population -- 266,000 people -- and killed 260 of them.
The virus has spread to Singapore and people who go to neighboring Malaysia to buy durian fruit may be helping to carry it, said Dr. Harold Townson of the Liverpool School of Tropical Medicine in Britain.
"Aedes albopictus is very common in the United States and Caribbean," Townson said. "There are risks it could be introduced here."
And Gubler noted that another species of mosquito, the dengue-carrying Aedes aegypti, is re-emerging in Latin America.
Aedes aegypti is the original carrier of Chikungunya -- whose name comes from a word in the Makonde language of Tanzania describing the stooped stance of victims.
Reporting by Maggie Fox; Editing by Julie Steenhuysen and John O'Callaghan