This has been one of Colorado’s worst years for the West Nile virus, and the toll may not be over, since the days are still warm enough for mosquitoes to come out and bite.
Most people who get West Nile virus never know they were infected, and those who do get sick typically have flu-like symptoms. In a small percentage of cases, though, the virus invades the brain or spinal cord, potentially causing disability or death.
As of Friday, the state had recorded 195 total cases, which is almost certainly a significant undercount since most people wouldn’t know to get tested. Hospitalizations were at their third-highest level since the state started counting in 2003, with 135 people receiving care for severe symptoms.
Deaths and cases in which the virus invaded the nervous system were at their second-highest level, with 122 people developing inflammation in the brain or spinal cord and 13 people dying. The only year with more severe cases was 2003, when 146 people were hospitalized, 622 had neuro-invasive infections and 66 died.
Mosquitoes thrive in warm, relatively moist summers, particularly if they followed a mild winter, said Dr. Jennifer House, deputy state epidemiologist and public health veterinarian at the Colorado Department of Public Health and Environment. But there’s also an element of chance, since only about one-fifth of people who get West Nile develop symptoms, and even fewer are sick enough to seek testing, she said.
“It’s a combination of all of the above,” she said. “We can never tell if we’re going to have a bad year or not.”
This year’s toll is similar to 2021’s, though people are still getting sick in October because it’s been relatively warm on the Front Range, House said. It’s difficult to know how climate change will affect the prevalence of West Nile virus, but it is likely to extend the season when people are vulnerable, she said. Mosquitoes generally don’t hibernate until temperatures consistently stay below 50 degrees.
“We don’t want to see any more cases, and certainly not any more deaths,” she said.
“There’s nothing we could do”
Audrey Moon’s father John Moon was one of the 13 people who died of West Nile in Colorado this year.
At first, he had general symptoms like a fever and lethargy, but the virus caused inflammation in his brain. He spent about a month on a ventilator before doctors determined he was unlikely to recover, and the family decided not to continue aggressive measures, she said. He died on Sept. 30, less than a week after his 70th birthday.
While he was older, he also loved his active life as a retiree in Denver and had just taken up paddleboarding when he got sick, Moon said. Ironically, one of the things he jokingly talked about loving most in Colorado was the lack of bugs, compared to what he’d been used to in Missouri, she said.
There’s no specific treatment for West Nile virus, so care focuses on managing symptoms. Moon said she hopes greater awareness of severe cases will help drive research on a vaccine or antiviral to prevent deaths like her father’s.
“It’s just maddening to me, now that he’s gone, that there’s nothing we could do,” she said.
When West Nile virus is fatal, it’s usually because of inflammation in the brain — encephalitis — or in the covering of the nerves in the brain or spinal cord — meningitis.
While older people are more likely to develop severe disease, a study following up with people who survived Colorado’s unusually large outbreak in 2003 found the average age of those who’d had meningitis was 48.
About half of patients who’d had encephalitis reported they still had symptoms three months later, as did 26% of meningitis patients and about one-fifth of those who’d had a fever but didn’t become seriously ill. The most common symptoms that lingered were muscle pain, muscle weakness and headaches.
Christopher Strain, of Loveland, was 37 when a West Nile infection turned into meningitis. It started with unexplained back pain on a Friday in late August 2017, and that Monday, he was in an intensive-care unit.
“By then I couldn’t use my right leg. My brain was so swollen, I thought I was on a spaceship,” he said.
Strain was released from the hospital after five weeks, but said he couldn’t move his right foot until around Halloween that year. He only stopped using a cane last year, and said he still “hobbles” a bit because of nerve damage in his leg.
Strain said he and his family are more careful about mosquitoes now, but there are limits to what they can control, since not everyone takes the same care keeping their property free of standing water. He said he doesn’t want his daughter to be afraid, but his experience showed how severe the consequences can be.
“You’re trying to figure out why your body is going through so much change and you’re looking for an answer, and the answer is a bug bite,” he said.
“You don’t even think twice about a mosquito”
A small percentage of people never recover fully after a West Nile infection.
Jeff Michie, who lived in Windsor at the time, got sick in late July 2017. It started with a severe headache, followed by tiredness and body aches that weren’t getting better. He and his wife Lisa Michie thought it was the flu, until one night he fell on the way to the bathroom and couldn’t move his legs to get up again.
The paralysis slowly moved further up his body, and at one point the only voluntary movement he could make was blinking, Jeff Michie said. It took two weeks to get an answer about what was causing his symptoms, and there wasn’t much the hospital could do other than keep him breathing on a ventilator, Lisa Michie said.
Their friends and family were “shocked” Jeff got so sick, because he was only 56 and ran multiple miles a day, Lisa Michie said. They’ve never gotten an answer to why the virus struck him that summer after a lifetime of outdoor activities, or why it made a healthy person so sick, she said.
“You don’t even think twice about a mosquito until it happens to you,” she said.
Most people who they’ve encountered through support groups for survivors have gotten better slowly, but that hasn’t happened for Jeff, who has feeling throughout his body but can’t move below the chest, Lisa Michie said. They moved to Vero Beach, Florida, after finding he felt better with warmer winters and could breathe and speak more easily at a lower altitude, she said.
Prevention is the only defense against West Nile virus, House said. Mosquitoes can breed in as little as a tablespoon of water, so it’s important to regularly check for standing water on your property, she said. Water can collect in pool covers, bird baths, planters or even furniture cushions that aren’t regularly disturbed.
People can also protect themselves by covering their skin and using repellants when they’re going to be outside, especially around dawn and dusk, House said.
Lisa Michie said she gets frustrated when people oppose efforts to kill mosquitoes because they’re more worried about the chemicals used than about viruses the bugs carry.
“People do die from this. It does change lives,” she said.
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