Record Number of West Nile Virus Infections Reported in US Cases of West Nile virus have been reported in every U.S. state except Hawaii so far this year. Research suggests that West Nile virus risks are higher due to climate change. Mosquitoes that carry the disease multiply in pools of standing water and thrive in warm temperatures. Both conditions are fueled by climate change, which is bringing heat and heavier downpours in areasbr of the U.S. A person with West Nile virus may experience fever, headache and swollen lymph glands. In some cases, it can worsen to a potentially deadly inflammation of the brain, a condition br called encephalitis. It can also cause meningitis. There is no vaccine for West Nile virus and drugs can only manage br the condition.