The first human case of West Nile virus in Weld County has been found near the Johnstown/Milliken area, the Weld County Department of Public Health and Environment reported Friday.
All three of the county’s mosquito testing zones have tested positive for West Nile virus and county health officials are urging residents to protect themselves from mosquito bites by wearing repellent and long sleeves and avoiding areas with standing water. He said it will be up to municipalities to decide if they will be more aggressive in their mosquito spraying programs this season.
The vector index — a number determined from the mosquito trapping and testing data — for the Johnstown/Milliken area is currently 2.3, while last year it was only 0.2 for the same area, health department spokesman Eric Aakko said. He said the average for all three zones in the county this year is 1.54, while the average for the three zones last year was only 0.2.
“When the vector index exceeds 0.5, the risk for human infection increases greatly,” said Mark Wallace, executive director for the heath department. “With the vector index high for all of the testing zones, we encourage residents to take precautions against mosquito bites.”
The Culex mosquito, known to spread West Nile virus, is trapped and tested to determine the risk of disease to humans. Some municipalities in Weld County have mosquito control programs that include spraying. However, these programs only reduce the number of mosquitoes and don’t eliminate all mosquitoes.
West Nile virus is carried by birds and transmitted by mosquitoes that bite the infected birds. Infected mosquitoes transmit the virus to humans, horses and birds.
West Nile virus symptoms may appear three to 14 days after infection. Initial symptoms include fever, headache, nausea and vomiting, muscle ache and weakness and rash. Symptoms of severe illness include high fever, stupor, disorientation, coma, tremors, muscle weakness, vision loss, paralysis and death.
About 75 percent to 80 percent of people show no signs or symptoms after getting bit by an infected mosquito, while about 20 percent will experience West Nile fever, which includes headaches and body aches, but will recover on their own, Aakko said.
He said about 1 percent of the population will experience severe illness, including inflammation of the brain or spinal cord, a high fever, disorientation and possibly paralysis.
Aakko said anyone experiencing symptoms should see their doctor and be tested for West Nile virus.
For more information on West Nile virus and mosquito bite prevention, visit www.weldhealth.org.