West Nile Virus Is on the Rise Across Israel. Here’s How You Can Stay Safe
Case numbers in Israel are at a 20-year high, possibly due to shifting weather patterns
West Nile virus is surging across Israel at a rate not seen since 2000. So far this summer, the Health Ministry has reported over 150 cases, including nearly a dozen fatalities, within only a month. Israel typically sees only several dozen cases throughout the summer, peaking between mid-August and mid-October.
Late last month, during routine monitoring at Ben-Gurion Airport and in Ramat Gan, the Ministry of Environmental Protection detected significant populations of mosquitoes carrying the virus. In response, the ministries swiftly began initiating mosquito spray operations and other preventative measures.
Dr. Yael Paran, head of the infectious diseases unit at Tel Aviv Sourasky Medical Center, told The Media Line that initial data hasn’t revealed whether this strain of West Nile virus is more dangerous than previous strains.
Dr. Yael Paran. (Courtesy)
We are seeing the numbers we normally see in a year in one month, and it is only June—much earlier than usual
“We see many more patients with West Nile virus, numbers unprecedented until now,” she said. “We are seeing the numbers we normally see in a year in one month, and it is only June—much earlier than usual.”
She said that the reasons behind the surge in cases remain unclear. One theory connects the rising case rate to this year’s uncommonly hot summer and wet and stormy winter. Pools of rainwater are the ideal habitat for female mosquitoes to lay their eggs, and the insects thrive in the summer heat.
The Israel Meteorological Service reported that this June’s temperatures exceeded the multiyear average by more than 5.5 degrees Fahrenheit (3 degrees Celsius). Israel experienced the hottest June day on record during intense heat waves over the first half of the month, with temperatures reaching 118.4° Fahrenheit (48° Celsius).
Dr. Eyal Leshem, director of the Center for Travel Medicine and Tropical Diseases at Sheba Medical Center, told The Media Line that scientific evidence has not proven a connection between climate change and the increased spread of West Nile virus.
Dr. Eyal Leshem. (Courtesy)
West Nile virus has a long history in Israel. According to the Health Ministry, the first recorded outbreak of the disease dates back to the 1954-1955 season, with another outbreak documented in 1957. Increased virus activity was also observed during the late 1970s and 1980s. In 1997, the virus was identified in birds in Israel for the first time. A significant outbreak followed in 1998, and more than 400 cases were reported in 2000.
How Does West Nile Virus Spread?
The virus spreads from animals to humans through mosquitoes, with no known human-to-human transmission. Mosquitoes acquire the virus from infected birds.
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Paran said that this year has seen a significant increase in the number of infected bird carcasses identified in Israel. Last month, approximately 120 bird carcasses were tested at the Central Virology Laboratory, with 36 testing positive—a tenfold increase compared to the previous year.
The virus is mainly spread by Culex mosquitoes, known as the common mosquito, which are distinct from Aedes albopictus, the Asian tiger mosquito that carries dengue fever.
According to Leshem, dengue cases have also occurred in Israel over the last two decades, primarily in individuals who contracted the disease overseas, such as in Thailand or South America. Recently, three cases were identified in Egypt’s Sinai Peninsula.
Symptoms and Treatment
Around 80% of those infected with West Nile virus don’t experience any symptoms. Those who do experience symptoms may develop a fever, headache, weakness, joint and muscle pain, inflammation of the eye membrane, rash, and sometimes nausea and diarrhea. In fewer than 1% of cases, the virus can cause acute inflammation of the brain (encephalitis) or inflammation of the brain lining (meningitis), which can result in death.
The disease is not dangerous for most people. However, those who are older or who are immunocompromised are at most significant risk for developing severe disease.
Paran said the virus is diagnosed via a blood or urine test, though sometimes a spinal tap is required.
There is no specific treatment for West Nile virus. Patients are given general pain relievers and, in severe cases, can be intubated.
Paran and her team at Sourasky are working on developing a treatment for the disease using interferon, a type of protein that bolsters the body’s immune response to the virus. Interferon therapy was previously tested during the COVID-19 pandemic.
The randomized controlled trial is being conducted at nearly all the hospitals in Israel’s center and north. “We hope we will see some improvement,” Paran said.
Meanwhile, the crucial focus remains on prevention—avoiding mosquito bites altogether.
Preventing Infection
Even a small amount of standing water can become a breeding ground for potentially infectious mosquitoes.
Walk around your home and remove any standing water from flower vases or planters
“Walk around your home and remove any standing water from flower vases or planters,” Leshem suggested. He also advised installing screens on windows and doors and stocking ponds with fish to naturally control mosquito larvae.
Using fans or air conditioning can also deter mosquitoes.
Leshem recommended contacting one’s local municipality to report standing water. He said that high-risk individuals should wear long sleeves and pants at night and spray themselves with mosquito repellent, ideally a DEET-based spray.
