What’s the buzz? West Nile virus

By Michaela Gibson Morris/NEMS Daily Journal

The kids may be back in school, but summer is still going strong for mosquitoes and West Nile virus.
“We are right in the middle of the most active time of the year,” for West Nile virus, said Dr. Paul Byers, deputy state epidemiologist. “Folks need to take precautions now, not later.”
Already, there have been 47 West Nile cases and one death confirmed by the Mississippi Department of Health through Wednesday, and August and September are usually the most active months for the virus.
“So far this year, it’s shaping up to be a pretty active year,” Byers said, noting the year 2011 totaled 52 confirmed cases.
Rankin County has the most cases so far with seven confirmed. To date, most of the cases have clustered in south and central
Mississippi. In Northeast Mississippi, Calhoun and Monroe counties have each had a case confirmed.
“It doesn’t matter if we haven’t identified cases in your county,” Byers said. “We know it can occur through the state.”
Symptoms
While there are countless mosquitoes, relatively few people get sick with West Nile virus
“Most people infected do not have any symptoms,” Byers said.
About 20 percent of the people who are infected will have some type of symptom, most of them mild, often with a slight fever or headache.
A small group of people who develop symptoms can have significant problems with neuro-invasive West Nile, developing meningitis – an infection of the spinal cord, encephalitis – an infection of the brain or flaccid paralysis.
“There is no antibiotic for West Nile virus,” said Dr. Mindy Prewitt, Tupelo infectious disease specialist. “Treatment is supportive care, and some patients may be sick for a long time.”
Symptoms of meningitis and encephalitis can include rapid onset of high fever, head and body aches, confusion and neck stiffness. Because there are different types of meningitis and encephalitis caused by different kinds of bacterias and viruses, people should seek medical attention quickly, Prewitt said.
Most of the people who develop the neuro-invasive form of West Nile are over 50.
“But anybody at any age can be infected,” Byers said. “Anybody of any age can have significant consequences. Across the board, all Mississippians should be protecting themselves.”
Why 2012?
Although 2002 remains far and away the high water mark for West Nile in Mississippi – with nearly 200 confirmed cases and a dozen deaths, 2012 is shaping up to be an active year.
“West Nile is becoming cyclical,” said Mississippi State University Professor Jerome Goddard, a medical entomologist. “It’s probably related to the susceptibility of birds. When an outbreak occurs, a majority of the birds in that area become immune to the virus, and the human cases go down for a few years until the bird population becomes susceptible again, leading to another outbreak.”
Birds serve as the reservoir for the virus; mosquitoes pass the virus between birds and to humans.
In Mississippi, the Southern house mosquito is the primary culprit in spreading West Nile. This mosquito actually loves hot, dry conditions, because it prefers small, stagnant pools of water that are rich in organic material, said Goddard, who spoke last week at an infection control conference at North Mississippi Medical Center in Tupelo.
Clogged gutters, tires, waste water sewers, pet water bowls, flower pot saucers and even bottle caps and other trash are ripe places for the mosquitoes to breed. Rains usually flush the Southern house mosquito larvae out of these places.
“June was totally dry, and it made West Nile worse,” Goddard said.
But just because the rains picked up in July doesn’t mean the risk of West Nile has abated. The adult Southern house mosquitoes that hatched during June aren’t affected by the rain.
“They’re still out there flying around,” Goddard said. If the rain slows down in August and September, as it often does, the breeding conditions will improve for the Southern house mosquito.
“Mosquitoes can transmit diseases,” Goddard said. “So it behooves you to try to avoid them.”
michaela.morris@journalinc.com