West Nile Virus cases confirmed in Fresno, CA and Baltimore, MD


The California Department of Public Health (CDPH) reported that nine Fresno County residents have tested positive for West Nile virus (WNV) infections so far this year, including three asymptomatic WNV-positive blood donors.

In Baltimore, the Maryland Department of Health (MDH) announced that an adult living in the Baltimore Metropolitan area has tested positive for the West Nile virus – the first confirmed human case of the virus in Maryland this year.

The West Nile virus is transmitted to humans by mosquitoes who have been infected by feeding on birds that have the virus. In rare instances, the virus may be spread from person to person through organ donation, blood transfusion, breastfeeding, or from pregnant mother to fetus.

According to the CDPH, Fresno County mosquito control districts have collected 216 samples of mosquitoes that have tested positive for WNV. “With confirmation of these cases and an increase in the number of mosquito collections testing positive for WNV, it is important that everyone take precautions to protect themselves and their families from mosquito bites,” says Katherine Ramirez, science education coordinator with the Consolidated Mosquito Abatement District.

Dr Rais Vohra, Fresno County Interim Health Officer, said, “These cases are a reminder that infections from mosquitoes continue to be a hazard. Please maintain vigilance and use the strategies that our partners are advocating to prevent mosquito bites and get medical attention if you are ill with symptoms of West Nile virus infection.”

“We are in the season when we start to see West Nile virus spread in Maryland,” said MDH Deputy Secretary for Public Health Services Dr. Jinlene Chan. “We urge people to be vigilant and take steps to avoid infection. Disease surveillance teams are closely monitoring for any signs of increased numbers of infected mosquitoes that may turn up in areas across the state.”

West Nile virus was detected in the United States for the first time in 1999. Health department officials said the disease affects the nervous system, and up to 80% of people who are infected will not display any signs of illness at all. Those who have underlying health conditions, however, could become seriously ill.

The CDPH encouraged residents to contact their local mosquito control district regarding standing water or mosquito problems, as well as to report any neglected swimming pools. “Neglected pools are a major source of mosquito production in urban and suburban areas,” an advisory said.

The CDPH told residents to practise what it calls the “Three Ds”:
1. Deter – Apply insect repellent containing DEET, picaridin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. Insect repellents should not be used on children under two months of age.
2. Dawn and Dusk – Mosquitoes usually bite in the early morning and evening, so it is important to wear proper clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep mosquitoes out. Repair or replace screens that have tears or holes.
3. Drain – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, by emptying flowerpots, buckets, and other water-holding containers. If you know of a swimming pool that is not being properly maintained, please contact your local mosquito control district.

The CDPH said Fresno County residents can find support regarding WNV concerns www.fresnocountymosquito.org, and https://westnile.ca.gov. Baltimore residents can call 1-877-463-6497 for a list of licensed rehabilitators or visit the Maryland Department of Natural Resources web site at DNR Wildlife pages.