West Nile Virus is spread through the bite of an infected mosquito after mosquitoes feed on infected birds.

Common Symptoms

• Fever
• Headache
• Body aches
• Fatigue
• Rash

Severe Symptoms

• High Fever
• Brain Swelling (encephalitis)
• Vision Loss
• Paralysis
• Coma
• Convulsions
• Death

Higher Risk Groups

Severe illness is more likely in:

• Adults over 50
• Individuals with weakened immune systems
• Young children

Prevent West Nile Virus Sources

One of the biggest risk factors for West Nile Virus in Merced County is green or unmaintained swimming pools.

Over the course of 1 month, a single neglected pool can produce 3 million Culex mosquitoes capable of spreading disease throughout a neighborhood.

Report to the District:

• Green or unmaintained swimming pools
• Stagnant water
• Neglected properties with mosquito activity

Dengue Fever is spread by invasive Aedes mosquitoes, aggressive daytime mosquitoes commonly found around homes and neighborhoods.

Unlike West Nile Virus mosquitoes, Aedes mosquitoes prefer breeding in small containers filled with water.

Common Symptoms

• High Fever
• Severe headache
• Pain behind the eyes
• Joint and muscle pain
• Nausea
• Rash

Severe Symptoms

• Severe stomach pain
• Persistence vomiting 
• Blood in urine, stool, or vomit
• Difficulty breathing
• Extreme fatigue, restlessness, or irritability
• Bruising under the skin

Most dengue cases in California are associated with travel outside the area. In Merced County, we have never experienced local transmission of Dengue Fever.

Prevent Dengue Mosquito Sources

Invasive Aedes mosquitoes capable of spreading Dengue Fever commonly reproduce in small water-filled containers around homes.

Empty Water Weekly From:

• Flower pots and saucers
• Buckets
• Pet bowls
• Tires
• Toys
• Bird baths
• Trash containers

Even small amounts of standing water can produce mosquitoes.