A “Health Advisory” issued a couple of weeks ago by the Pennsylvania Department of Health Secretary, Dr. Rachel Levine (who is, by the way, a pediatrician), alerted health professionals about the increased prevalence of West Nile Virus (WNV) in the state:
- WNV-positive mosquito pool counts are at an all-time high this season
- Health care providers should have a heightened clinical suspicion for West Nile infection in persons with clinically compatible symptoms
West Nile Virus infections are spread by mosquitos — vectors that are more active, efficiently reproduce, and aggressively bite during the warm and wet summer months:
In Pennsylvania, WNV is the most commonly reported locally-acquired arbovirus and is most commonly seen during the months of July through September. Risk continues until the first hard frost. Most human WNV infections (80%) are asymptomatic. Approximately 20% of infections result in a non-specific febrile illness (West Nile fever), and <1% infections develop into severe neuroinvasive disease (e.g., meningitis, encephalitis, acute flaccid paralysis, etc.).
Neuroinvasive disease is more likely to occur in patients >50 years of age or those with compromised immunity.
The symptoms affecting 20% of infected people are not specific, indeed: fever, headache, body ache, nausea and vomiting, and sometimes a body rash and swollen lymph nodes. Acute symptoms typically last several days to a week or two and resolve completely without treatment. More serious symptoms indicating involvement of the nervous system (meningoencephalitis) — disorientation, coma, seizures, high fever, neck stiffness, muscle weakness, numbness, and paralysis — can last several weeks and lead to permanent disability and death. In light of recent news coverage, let’s repeat: 80% of people who are bitten by an infected mosquito will not have symptoms.
Trista Thurston provides a local update:
Across Pennsylvania, 57 of the state’s 67 counties have had positive samples for the disease. The state Department of Health has also announced that 15 counties have had infected dead birds.
There have been 47 total positives in Allegheny County and six in Washington County, according to the state.
Allegheny County’s one human case of the virus was reported in late July, according to the state’s West Nile Virus Control program. County officials previously said a Penn Hills man in his 70s was diagnosed in mid-July. He was taken to the hospital when he was first experiencing symptoms but has since been released to recover at home.
The Allegheny County Health Department collected positive samples in five neighborhoods: Hazelwood, Southside Flats, Southside Slopes, Mt. Washington and Beltzhoover.
We’ve covered the best ways to repel insects, and, more recently, the safety of using commercial products containing DEET before on The PediaBlog. Pennsylvania’s West Nile Virus Control Plan highlights the personal protective measures parents can take to help their children and themselves avoid mosquito bites:
Protective clothing should be worn when mosquitoes are actively biting: long pants, long sleeve shirts, socks. Many mosquito species that transmit WNV are most active at dawn and dusk.
Use a mosquito repellant.
- DEET is safe and most effective. The percent DEET concentration on a product indicates relative duration of protection for mosquitoes (e.g., a product containing 20% DEET will remain effective for more time than a product containing 10% DEET). DEET should not be used on children under 2 months of age.
- Repellants containing Picaridin, oil of lemon eucalyptus and IR3535 provide protection similar to products with low DEET concentration. Oil of lemon eucalyptus should not be used on children under 3 years of age.
- Always apply repellant for young children. Do not let them apply by themselves. Apply repellant to your hands, and use your hands to apply repellant onto child’s skin.
- Store repellant out of reach of young children.
- Wash treated skin and clothing when returning indoors.
Mosquito netting can be used to protect young children and infants that are outdoors.
Ensure doors and windows have tight-fitting screens. Repair or replace screens with tears or holes. The ordinary window screen with 16×16 or 14×18 meshes to the inch will keep out most mosquitoes.
Vitamin B, ultrasonic devices, incense and bug zappers have not been shown to be effective in preventing mosquito bites.
Most mosquitos live, breed, bite, and die close (only a few hundred feet or so) to where they emerge. Therefore, making sure that water does not collect near your home and provide breeding opportunities can also be effective in preventing mosquito bites:
> Maintain good screens on your windows and doors to keep infected mosquitoes out.
> Regularly empty any outside containers, or drill drainage holes in their bottoms.
> Turn over plastic wading pools and wheelbarrows when not in use.
> Clean clogged roof gutters that may allow the pooling of rain water.
> Do not allow water to stagnate in either bird baths or ornamental ponds.
> Clean and chlorinate swimming pools and remove standing water from pool covers.
> Use landscaping to eliminate standing water that routinely collects on your property.
> Remove discarded tires from your property as they make an excellent larva habitat.
> For standing water that can’t be eliminated, residents can buy either Bacillus thuringiensis israelensis (Bti), or Bacillus sphaericus (Bsp) tablets at any lawn and garden store. After such a tablet is thrown into the water the bacteria will infect and kill any mosquito larvae present, but the water will remain safe for people, pets, aquatic life and plants.