Everything You Need to Know About the West Nile Fever Scaring Israelis

There is no vaccine or cure, but the good news is that the disease, which is spread by mosquitoes, usually goes away without treatment

Ido Efrati
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The Sorek stream
The Sorek stream, where mosquitoes carrying the West Nile Virus, have been found.Credit: Emil Salman
Ido Efrati

What is West Nile fever?

People get West Nile fever by mosquito bites, and in Israel it's from the Culex mosquito. That means that mosquito season is the time to take precautions. West Nile is one of about 70 flavivirus strains, most of which are transmitted by insect bites The virus' natural host is birds. The viral cycle actually involves only birds and viruses, but if mammals — humans, for example — get bitten by an infected mosquito, they can also develop the virus.

Who is vulnerable?

Among humans, West Nile Virus affects mainly the elderly and those with impaired immune systems, including diabetics. Children up to age 3 rarely get the disease, and if they do come down with it, it's mild. Pregnant women are not at higher risk than other people. Fetal infection is extremely rare and there have been no such recorded cases in Israel. The virus cannot be contracted by having contact with an infected person. The incubation period can range from five to 21 days, but not everyone develops symptoms.

How is the virus diagnosed?

Through a lab test. The Health Ministry has facilities to diagnose the virus at the Sheba Medical Center at Tel Hashomer and at Rambam Medical Center in Haifa. Test results are available within a few days after the hospital receives the sample.

Where is the virus prevalent in Israel?

Anywhere that there are Culex mosquitos, but mainly along the country's Mediterranean coastline and in the Arava valley, running from the Dead Sea to Eilat. Mosquitos carrying the virus have been detected this summer in the regional councils of Emek Hama’ayanot, Gezer, Megilot, Mateh Yehuda, Menashe, Megiddo, Alona, Gush Etzion and Gilboa, in addition to the communities of Mazkeret Batya, Caesarea and Pardes Hannah-Karkur. The prevalence of the virus peaks in Israel between August and mid-October. This year 74 cases have been diagnosed, including 14 serious cases.

How serious is West Nile Virus?

Most people remain asymptomatic. For those who do feel it, symptoms are similar to the flu: fever, headache, weakness, joint and muscle pain, conjunctivitis, rash and sometimes nausea and diarrhea, which resolve on their own, but in about 1 percent of cases, there can be complications, including encephalitis and meningitis, which can be fatal.

Is there a cure?

No, nor is there a vaccine. Serious cases require hospitalization for treatment of the symptoms. On the whole, West Nile fever must be addressed through prevention — by avoiding getting bitten. That includes wearing long sleeves and insect repellent and elimination of standing water where mosquitos breed.

Is this year's season the same as prior ones?

West Nile Virus has been known about since the 1950s. It tends to peak every few years. The year 2000 was a bad one, with 417 cases in Israel, including 324 patients who required hospitalization and 35 who died. Since then, dozens of patients have been diagnosed every year. This year the number is higher than the average.