Africa Germ, Asian Insect Meet in Italy, Spur Disease (Update1)
By Jason Gale
Sept. 25 (Bloomberg) -- A virus from Africa, a mosquito from Asia and a tourist from India met one day this summer on the Italian seaside, showing how globalization hastens the spread of disease from one continent to another.
Almost 270 people in Italy's province of Ravenna may have been infected with chikungunya, a virus that causes fever, rash and joint pain, since it arrived with a tourist three months ago. The outbreak was caused by the same viral strain that sickened about 235,000 people on Reunion island in the Indian Ocean last year, says an Italian virologist investigating the episode.
Now Italy is threatened by a contagious illness that may also spread elsewhere in Europe and North America the same way it got to Ravenna -- through an infected traveler. There were 2.1 billion airplane passengers last year, driving the spread of new diseases that are emerging at ``an unprecedented rate,'' the World Health Organization said last month.
``We are in a world where things are whizzing around so fast we inevitably are going to see more and more of this kind of thing happening,'' said Paul Reiter, director of the insects and infectious diseases unit at the Pasteur Institute in Paris.
At least 39 new pathogens have been identified during the past 40 years, the WHO said in its 2007 World Health Report last month. They include the HIV virus that causes AIDS, Ebola hemorrhagic fever, Marburg fever and SARS -- the respiratory infection that cost Asian businesses an estimated $60 billion in 2003, or more than $2 million per person infected.
`More Expensive'
Bugs that have infected people for ``thousands of years'' in local areas are now causing disease on an international scale, says Duane Gubler, director of the University of Hawaii's Asia- Pacific Institute of Tropical Medicine and Infectious Diseases. Epidemics resulting from ``globalization are going to be progressively more expensive,'' he says.
First described by doctors in Tanzania in 1953, chikungunya regularly causes epidemics in 23 countries in Africa, Asia and the Pacific. Until last month, Europe had only recorded cases in travelers who returned with the infection and didn't pass it on.
Scientists say chikungunya, for which there is no vaccine or specific treatment, could become established in parts of Europe and the Americas as a result of travel and commerce. Trade in used tires, which harbor insect larvae in trapped rainwater, has allowed the Asian tiger mosquito, which can transmit the virus, to colonize areas like the French Riviera, Florida and the Caribbean over the past 30 years.
Tire Trade
Tires from a single source in Atlanta may have introduced the insect, known scientifically as Aedes albopictus, to the northeast Italian city of Padua in 1991, according to the U.S. Centers for Disease Control and Prevention.
The species is now in nine of Italy's 21 regions, proving a receptive host for chikungunya, dengue -- a more serious disease that can cause lethal hemorrhaging -- and at least five other viruses.
Italy's chikungunya outbreak probably started with a man who arrived on June 21 and developed symptoms two days later when he was in the northeastern town of Castiglione di Cervia on Italy's eastern Adriatic coast, the European Centre for Disease Prevention and Control in Stockholm said in a report this month.
His arrival coincided with ``a very hot summer'' that favored mosquito-breeding, said Isabelle Schuffenecker, a biologist with France's national reference center for arboviruses and viral hemorrhagic fevers in Lyon. ``All the conditions were there to start this phenomenon.''
Genetic sequencing traced the virus to an outbreak in India that had caused more than 1.25 million suspected cases last year, and before that to an epidemic in a group of islands in the western Indian Ocean that began in late 2004, said Loredana Nicoletti, a virologist who helped diagnose more than 100 chikungunya cases for Italy's health ministry.
Epidemic Not Over
Test results are pending on samples from the most recent suspected cases in Italy, and the epidemic won't be declared over for at least two more weeks, Nicoletti said yesterday in a telephone interview from Rome.
Laboratory tests have confirmed 101 of the 267 suspected cases, ECDC spokesman Ben Duncan said today.
The strain, which came from southern, central and eastern Africa, mutated slightly while on Reunion, a French territory about 800 kilometers (500 miles) east of Madagascar. The genetic change may have enabled the virus to replicate faster in the Asian mosquito and be capable of infecting humans about four to five days earlier than it otherwise would have, according to Schuffenecker, who studied cases there.
Mutant Bug
The mutation occurred about three months before a surge in infections at the end of 2005, Schuffenecker and colleagues said in a study published in PLoS Medicine in July 2006. About 12,400 cases were reported on the island of 770,000 people that year. More than 230,000 infections occurred in the first four months of 2006, some linked to fatal brain disease and liver failure.
Efforts to control mosquito-breeding, aided by cooler winter weather, and closer surveillance of chikungunya cases may break the chain of transmission over the next few months, Schuffenecker said.
``At least this year, I think we will be able to contain transmission, but what of next summer?'' Schuffenecker said. ``That's the question.''
To contact the reporter on this story: Jason Gale in Singapore at j.gale@bloomberg.net .
Last Updated: September 25, 2007 05:55 EDT
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