The tropical disease dengue fever is on the increase in Israel and it's only a matter of time until it becomes actively infectious here, according to a local expert.
Dengue fever (also known as breakbone fever ) is a virus-caused disease that is spread by mosquitoes. Prof. Eli Schwartz, director of the Center for Travel Medicine and Tropical Diseases at the Sheba Medical Center, Tel Hashomer, recently published an article in the American journal Emerging Infectious Diseases.
Schwartz noted that there has been an upswing in cases of Israelis stricken by the virus abroad and then diagnosed on their return home. The rise in such cases, in areas close to where the mosquito's presence in Israel is also increasing, multiplies the risk that the disease will become actively infectious here, although locally-spread cases have yet to be reported.
Asian tiger mosquito are believed to have found their way to northern Israel in 2002 in cars imported through Eastern Europe; water in the tires provided the mosquitoes with breeding grounds. They spread from the north to the coast, and in 2010 they were even reported in Jerusalem.
While the bite of the Asian tiger mosquito is only slightly more painful than that of the regular variety, the dengue virus may cause gastrointestinal bleeding and loss of body fluids, as well as anaphylactic shock (similar to a life-threatening allergic reaction ) and death.
Only one Israeli death due to the disease has been reported over the last decade, but the growth of tourism to the Far East has led to hundreds of cases being diagnosed in Israel each year, including dozens of severe cases requiring hospitalization.
Thailand is the most dangerous country when it comes to dengue fever, and 120,000 Israelis visit there each year.
Schwartz's team also reported on the Israeli outbreak of another viral disease spread by the Asian tiger mosquito - Chikungunya - which causes fever and headaches, and is likely to lead to continued joint pain and irreversible lung damage.
The scientists mapped the mosquitoes' spread in the country, finding that they were present in the areas inhabited by the Israelis who were infected abroad by dengue and Chikungunya between 2008 and 2010, according to the records of the Health Ministry's National Virological Laboratory for tropical diseases at the Sheba Medical Center.
The mosquitoes' main concentrations are in the Haifa area; Tel Aviv and other cities in the center of the country; Modi'in; and Jerusalem. Of the 42 dengue sufferers diagnosed during this time, 27 (66 percent ) lived in areas where the mosquitoes were found; of the 15 diagnosed with Chikungunya, 12 (80 percent ) lived in such areas.
"Dengue fever has the potential to become active in Israel as a result of the encounter between the mosquitoes and disease carriers with the virus in their bloodstreams," warns Prof. Schwartz. "Doctors must be aware of this possibility."
Calls for quarantine
The researchers also call for the quarantine of people suspected of dengue or Chikungunya infections for up to the five-day incubation period before symptoms appear, in order to prevent outbreaks of the disease within Israel.
In another recent report in the Emerging Infectious Diseases journal, Schwartz and his research team refuted a theory that infection by one of the four types of dengue fever after infection by a different type increases the possibility of developing a more severe case of the disease.
The report by the Schwartz team follows recent news showing that the common tropical disease malaria, spread by the Anopheles mosquito, may also be spreading in our area. Considered the main cause of death in Africa, the disease broke out in Greece in September 2011, and Israeli tourists were advised to take steps to prevent being bitten by mosquitoes there.
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