West Nile virus striking valley earlier than normal

With the addition of two new patients, the Las Vegas Valley has four of the nation’s 14 reported cases of West Nile virus, health officials say.

On Wednesday, the Southern Nevada Health District reported the area’s first death from the virus; there has been one other death nationally in 2013, according to the Centers for Disease Control and Prevention.

Health officials citing federal privacy laws would not disclose whether the most recent West Nile-related death involved a man or a woman or where he or she died. In early July, the health district revealed a 60-year-old woman had fallen severely ill from the virus. The district also reported then that a 70-year-old man contracted the disease but his condition was not as serious and he was not hospitalized.

The two new cases involve a 77-year-old man and an 87-year-old woman. Each has the serious neuroinvasive form of the virus that affects the nervous system and can cause encephalitis, an inflammation of the brain, and meningitis, which causes inflammation of the membrane around the brain and spinal cord.

Devin Barrett, a senior disease investigator for the health district, said cases of the virus have been reported earlier this year in the Las Vegas Valley, but she has no concrete explanation for why.

“Normally we get the bulk of our cases in August and September,” Barrett said. “Who knows what’s going to happen? If our typical trend continues, this year will be higher than normal for us.”

Last year there were eight cases of the virus reported in Southern Nevada, three less than in 2011.

Clark County has had five West Nile-related deaths since 2003.

Dr. Alan Greenberg, an infectious disease specialist at University Medical Center, said it could be that the large number of foreclosed homes in Clark County with standing pools of water on their grounds is helping to breed mosquitoes.

Mosquitoes pick up the virus from infected birds and transmit it to humans, birds and other animals they bite.

Although Barrett agreed that abandoned homes could play a role, she noted that Las Vegas has had large numbers of foreclosed houses in the recent past without seeing an uptick in West Nile virus.

“I know more doctors are testing for it now because I’ve seen the lab results,” Barrett said. “That also may be playing a role. I’m not sure there is any one answer.”

West Nile-positive mosquitoes have been detected in the 89014 ZIP code, but Barrett said the new cases come from outside that area. “We believe that the mosquitoes are throughout the area,” she said.

Greenberg stressed there is no West Nile virus vaccine available for people. He pointed out, however, that the vast majority of people, as many as 80 percent, who become infected with the virus have no symptoms. About one in five who are infected will develop a fever with a headache, joint pains, vomiting, diarrhea or rash. Most of these people will recover completely, though fatigue and weakness can last for weeks or months.

Less than 1 percent of those who are infected will develop encephalitis or meningitis, which can include paralysis and seizures as well as death, Greenberg said.

The patients who are hospitalized can only receive supportive treatment, such as intravenous fluids, pain medication and nursing care. “There’s not much we can do,” Greenberg said.

“It really boils down to how well your immune system fights it off,” Barrett said. “That’s why prevention from mosquito bites is so important.”

Long-sleeve shirts and long pants, she said, should be worn at dawn and dusk, when mosquitoes do their feeding. People also should use mosquito repellent containing DEET. Swimming pools should be cleaned regularly, and when water is seen outside in such places as pots, wheelbarrows and tires, it should be eliminated.

Contact Paul Harasim pharasim@reviewjournal.com or 702-387-2908.