A new West Nile virus detection has been confirmed in Mobile County, with six sentinel chickens monitored by the Mobile County Health Department’s Vector Services program testing positive for the mosquito-borne illness.
The positives came from coops in three ZIP code areas: one chicken in 36509, three in 36582 and two in 36605. The results have been confirmed by laboratory testing, according to Dr. Kevin Michaels, Health Officer for Mobile County.
The findings extend a season in which West Nile virus has now been identified in several different parts of the county. The health department reported earlier detections in the 36605, 36613, 36575 and 36587 areas, and the latest results add the 36509 and 36582 areas while returning a repeat positive in 36605. Taken together, the pattern indicates the virus is circulating broadly rather than in a single pocket.
The Health Department’s Response
“West Nile virus is present in our county, and this detection is an important reminder for residents to protect themselves from mosquito bites,” Michaels said. “Vector Services will increase mosquito-control activity in and around these areas, continue monitoring our sentinel chicken flocks, and work to identify mosquito populations that may be carrying the virus.”
MCHD Vector Services will conduct additional spraying, door-to-door surveys in nearby areas, and adult mosquito trapping and testing for West Nile virus.
Each of those steps serves a distinct purpose. Spraying reduces the population of adult mosquitoes already capable of transmitting the virus. Door-to-door surveys let crews look for breeding habitat on private property — the containers, clogged gutters and low spots that produce mosquitoes a few yards from where people sleep — and give residents direct information about what is happening nearby. Trapping and testing adult mosquitoes tells the department which species are carrying the virus and in what numbers, which in turn shapes where and how often crews return.
How to Reduce Your Risk
Residents, especially those taking part in outdoor activities, are encouraged to take simple precautions to reduce mosquito bites:
- Use an Environmental Protection Agency-registered insect repellent containing DEET, or another approved active ingredient.
- Wear long-sleeved shirts and long pants when outdoors, particularly around dawn and dusk.
- Stay and sleep in places with air conditioning or intact window and door screens.
- Empty, cover, clean, or treat containers that hold standing water around homes, yards, worksites, and outdoor-event locations.
The last item is the one most often underestimated. Mosquitoes can breed in very small amounts of standing water, including water found in buckets, flowerpots, tires, birdbaths, pet bowls, gutters, tarps and outdoor containers. A saucer beneath a potted plant or the folded lip of a tarp can hold enough water to produce mosquitoes, and because the species involved often do not travel far, the insects biting someone in a backyard were frequently produced in that same yard.
Emptying and scrubbing containers weekly interrupts the cycle. Turning over wheelbarrows and buckets, changing birdbath water, keeping gutters clear and storing tires under cover all remove habitat before larvae can mature. Repellent and long sleeves address the mosquitoes that already exist; source reduction addresses the next generation.
Choosing and Using Repellent
The advice to use an EPA-registered repellent is more specific than it sounds. Registration means the product has been reviewed for both effectiveness and safety when used as directed, and registered products carry an EPA number on the label along with instructions on how often to reapply. DEET is the best known of the registered active ingredients, and several others are also registered for use against mosquitoes.
Higher concentrations of an active ingredient generally extend how long a single application lasts rather than making it more effective minute to minute, so a lower-concentration product reapplied on schedule can work as well as a stronger one left on all day. Repellent belongs on exposed skin and, where the label allows, on clothing; it should be applied after sunscreen rather than before, and washed off once indoors. Parents should follow the age guidance printed on the label, which differs from product to product.
What West Nile Virus Is
West Nile virus is maintained in a cycle between birds and mosquitoes. Mosquitoes become infected when they feed on infected birds and can then transmit the virus to people, horses and other animals through subsequent bites. People and horses are what epidemiologists call dead-end hosts — they can become sick, but they do not develop enough virus in their blood to infect a mosquito that bites them afterward, so they do not carry the transmission cycle forward.
Most people infected with West Nile virus do not develop symptoms. Some experience fever, headache, body aches, nausea, vomiting or rash. In rare cases the infection causes serious neurologic illness, including high fever, severe headache, stiff neck, confusion, muscle weakness, disorientation, tremors, paralysis or seizures. Anyone experiencing severe symptoms should seek medical attention promptly.
Because the great majority of infections produce no symptoms at all, confirmed human cases in any community represent only a fraction of actual infections. That is one of the reasons public health agencies rely on animal and mosquito surveillance rather than waiting for people to fall ill.
West Nile virus cannot spread from person to person or from horses to people. Horses can be vaccinated against the virus; no vaccine is currently available for humans. Horse owners in areas with confirmed circulation are generally advised to keep equine vaccinations current, since horses can develop severe neurologic disease.
The risk for mosquito-borne encephalitis viruses is generally greatest from August until the first fall freeze. That places the current detections squarely inside the highest-risk stretch of the year on the Gulf Coast, where warm, wet conditions persist well into autumn and a hard freeze typically arrives late.
What a Sentinel Chicken Program Does
Since 1985, MCHD Vector Services has monitored sentinel poultry flocks placed strategically across Mobile County to detect mosquito-borne viruses. That four-decade record makes the program one of the longer-running surveillance efforts of its kind in the region.
The method takes advantage of the same biology that drives the virus in the wild. Chickens are attractive to the mosquito species that feed on birds, and when an infected mosquito bites one, the bird develops detectable antibodies. Chickens do not become seriously ill from West Nile virus and, like people and horses, do not pass it on. In practice they function as biological samplers, quietly recording whether infected mosquitoes are active at a fixed location.
Blood samples are collected from the sentinel chickens each Monday and sent to a laboratory for testing, with results typically available later in the week. That weekly rhythm is why detections tend to be announced in clusters and why the department can speak with precision about where and roughly when the virus turned up.
In addition to monitoring 13 sentinel chicken coops, Vector Services traps and tests mosquitoes for West Nile virus, Eastern equine encephalitis and St. Louis encephalitis. Those three viruses circulate in overlapping bird-and-mosquito cycles along the Gulf Coast, and a single trapping program can screen for all of them.
Why ZIP Codes Instead of Addresses
The department reports sentinel results by ZIP code rather than by street location. The practice protects the property owners who host coops and reflects how mosquito control actually works: a positive result does not mean risk is confined to one yard, and it does not mean the surrounding area is uniformly dangerous. Mosquitoes range across neighborhoods, and a positive chicken indicates infected mosquitoes were active somewhere within flight distance during the sampling period.
The practical takeaway for residents is that a ZIP code named in a detection is where control crews will concentrate first, not a boundary line for personal precautions. With positives now recorded in six ZIP code areas across the county this season, the sensible assumption countywide is that West Nile virus is present and that bite prevention is worthwhile everywhere.
Standing Water After a Wet Stretch
The weeks after heavy rain are when container habitat is most productive. Mosquito eggs laid in and around dry containers can survive for extended periods and hatch when water returns, which is why a single soaking rain can be followed within days by a noticeable increase in biting activity.
A short walk around a property is usually enough to find the problem spots. Common offenders include tarps over boats and woodpiles, children’s toys and wading pools, trash-can lids, unused flowerpots and saucers, corrugated downspout extensions, tree holes, clogged gutters, boat covers and, most persistently, discarded tires, which hold water, resist drying and are among the most efficient mosquito producers around a home.
Reporting a Problem and Getting Help
Residents who want to report a mosquito concern can contact MCHD Vector Services at 251-690-8124. Additional information about mosquito control, along with an online service-request portal for mosquito and rodent concerns, is available through the health department’s website.
Reports from the public are more useful to the program than they may appear. Complaints help crews identify breeding sites and neighborhoods with heavy activity that trapping alone might miss, and they can prompt inspections of properties that would not otherwise be visited.
With sentinel testing continuing weekly and the highest-risk period running until the first hard freeze, further detections are possible before the season closes. Health officials’ advice does not change with each new positive result: use repellent, cover up at dawn and dusk, keep screens intact, and drain standing water. Anyone who develops a high fever, a severe headache, a stiff neck, confusion or unexplained muscle weakness should seek medical attention promptly.