Experts say risk for West Nile infection low as cases mount
As the count of new West Nile virus cases continues to grow in Michigan and across the country, experts state the risk for infection is low.
As of Friday, 57 cases in Michigan had been attributed to West Nile virus as well as three deaths: One in Washtenaw County, one in Wayne County and one in the city of Detroit. About 88 percent of the cases were neuroinvasive, indicating the severest symptoms of the disease.
The Culex mosquito, which is responsible for transmitting West Nile virus from birds to humans.
The Associated Press
Public health experts maintain that the risk for exhibiting severe symptoms associated with West Nile is low.
About 80 percent of people bitten by an infected mosquito don’t exhibit symptoms.
One out of five people bitten by a mosquito infected with West Nile virus will get sick. Of those that get sick, one out of 150 people may develop serious, neurologic forms of the disease, including meningitis and/or encephalitis.
The mortality rate for those that are severely ill is about 10 to 11 percent.
Meningitis is an infection of the lining of the brain and spinal cord. Encephalitis is an infection of brain tissue. One or both can occur in the most severe cases of West Nile virus.
Milder symptoms of the disease include flu-like symptoms. Signs a person should seek the care of a medical provider include the inability to control a fever, unable to hold liquids down and neurologic signs like muscle weakness, shaking and neck stiffness.
West Nile was first introduced into the U.S. in New York in 1999, when seven people died and 62 people were sickened.
The virus hit Michigan in 2002, when 51 people died and there were 614 cases of the disease, according to data from the Centers for Disease Control and Prevention. It’s been the biggest death toll in Michigan from the virus since that year.
The CDC has been collecting data on West Nile Virus since 1999. However, experts state there’s not enough data to determine trends at this point.
“The problems with any kind of West Nile study … it’s never really stayed in one place long enough to study it,” said Dr. Sandro Cinti, associate professor of infectious diseases at the University of Michigan Medical School.
There are vaccines for West Nile virus for horses, but none for humans. Persons admitted to the hospital for the disease can only receive support treatment.
“The request to the vaccine makers has not been really strong for a vaccine,” said Dr. Eden V. Wells, a clinical associate professor of epidemiology and an associate director of Preventive Medicine Residency at the U-M School of Public Health.
“That’s generally a problem,” Cinti said of the need for a vaccine for certain diseases in general. “There’s either zero demand or full demand.”
A recent survey by AnnArbor.com found most people are somewhat worried about West Nile virus.
Wells called West Nile virus “endemic” at this point.
“I was listening to some federal discussion on this last week,” Wells said. “If the disease is increasing and persists to where there is continued public health impact, there’s more of a call for that. … I think only time will tell about how much of a call there will be.”
Warm weather favorable to the growth and development of the Culex mosquito responsible for transmitting the virus from birds to people has fostered a population experts this season previously said was "suitable for an epidemic" of the virus.
Cinti said the ratio of severe neurological disease to mild disease from the virus is an indicator. This year, about half of the reported cases of West Nile virus nationwide are neuroinvasive.
“The question will be when this settles, are we seeing more severe disease?” Cinti said.
Municipalities in southeastern Michigan don’t fund mosquito control programs. However, the state monitors a number of mosquito pools in some counties. Birds, which are the host species for the virus, also are tracked.
People over the age of 50, or work outdoors in the morning or evening are at a higher risk for West Nile virus.
Wells said the growing number of cases should not be a source of panic, but a sign that it’s important to reduce the chance of exposure to a mosquito bite by taking measures recommended by health officials:
- Make sure window and door screens aren’t broken to keep mosquitoes outside
- Empty containers with standing water
- When outdoors, apply insect repellent that contains DEET or other approved repellent to exposed skin
- Wear long-sleeved shirts and long pants when outside
Amy Biolchini covers Washtenaw County, health and environmental issues for AnnArbor.com. Reach her at (734) 623-2552, amybiolchini@annarbor.com or on Twitter.
Comments
Kea
Mon, Aug 27, 2012 : 2:53 a.m.
"Of those that get sick, one out of 150 people may develop serious, neurologic forms of the disease, including meningitis and/or encephalitis. " Actually, it's one out of 150 of those that get infected (not get sick) that develop the neuroinvasive form of the disease.
Tru2Blu76
Mon, Aug 27, 2012 : 1:44 a.m.
1. "About 88 percent of the cases were neuroinvasive, indicating the severest symptoms of the disease." 2. "About 80 percent of people bitten by an infected mosquito don't exhibit symptoms." THESE TWO STATEMENTS ARE MATHEMATICALLY IMPOSSIBLE WHEN APPLIED TO THE SAME DISEASE - and this is the kind of "public information article" you're publishing. I was surprised the first time I heard someone say they had stopped reading AnnArbor.com because of the low quality. I am not surprised now that I've heard that a few times from more people (some educators included). There has actually been a drop off (sometimes in key articles) in the quality of journalism at/in/from Ann Arbor.com. And lets continue a bit with statistics: even a non-expert like myself knows that 57 cases of a disease in a total population (Michigan's population) of 9 million is a VERY SMALL DEAL. West Nile Virus isn't harmless, but it's only about a deadly as swimming - which produced 43 accidental deaths in the first eight months of 2011 (and five people died in swimming accidents in one weekend at the end of August last year). So there's your statistically accurate comparison which shows West Nile Virus is a tiny threat to our health and lives. To publish anything which suggests otherwise is reckless and irresponsible (possibly due to incompetence). The only mistake readers' comments suggests is that they unwittingly accept AnnArbor.com as a reliable source of information. What this article amounts to is more like proof of the opposite and I seriously hope you good people will take this seriously. If you have staff monitoring comments: then you should already know that those comments reflect confusion and ask for clearer information. You can't blame readers because it's on AnnArbor.com. I have to say: I'm very concerned because I had faith in AnnArbor.com and want very much for this city to have a great news source.
Amy Biolchini
Mon, Aug 27, 2012 : 3:03 p.m.
Tru2Blu76, health officials state that 20 percent, or one out of five, people bitten by a mosquito infected with West Nile virus may get sick. Of those that get sick, one out of 150 people may develop serious, neurologic forms of the disease, including meningitis and/or encephalitis. Those numbers are guidelines to assess the risk of infection. Here's what's happening this season: Of the 57 cases of West Nile virus reported in Michigan as of Aug. 22, 50 cases, or 88 percent of them, were the neuroinvasive forms of the disease, according to data from the Michigan Department of Community Health.
Tru2Blu76
Mon, Aug 27, 2012 : 3:42 a.m.
Thank you Kea but the full sentence at the end of paragraph 2 (about reported cases of infection) reads: "About 88 percent of the cases were neuroinvasive, indicating the severest symptoms of the disease." Not THOSE cases, you see, meaning this sentence is incorrectly written. This, I still say, is bad journalism: writers should know how to write! I'm mostly upset because I've defended AnnArbor.com and hoped they would become at least as worthy of representing this town as the Ann Arbor News once was. Also - it's not like I'm alone in my disappointment: look at the comments strewn after many articles and you'll see they reflect similar conclusions and feelings. (Also, they sometimes reflect a lot of confusion wrought by the poor writing in the articles.)
Kea
Mon, Aug 27, 2012 : 2:57 a.m.
It's 88% of the REPORTED cases that were neuroinvasive. Obviously, most cases aren't reported.
JRW
Mon, Aug 27, 2012 : 12:01 a.m.
WHY don't any of these articles SPECIFICALLY identify where these cases of WNV are located in Washtenaw County???? What is the problem? This article provides all kinds of data but NOT the specific cities where the deaths occurred in three counties, and the cities where the cases are located in Washtenaw County. What is the problem???
mars
Mon, Aug 27, 2012 : 4:06 p.m.
The health department has a duty to protect the privacy of the patients. Thus, they are rightfully hesitant to give details about the specifics of a patient (age, residence, etc.) - especially when those details are not relevant. Why does it matter to you? West Nile virus is endemic here. Unless you have had it before, you can assume that you are at risk anywhere in the county.
Amy Biolchini
Mon, Aug 27, 2012 : 2:55 p.m.
JRW, public health officials at the state and county level will not release the exact locations of the cases, using the reasoning that because the virus is present in area bird and mosquito populations, everyone should take precautions. If we had more specific information as to where the cases were reported, we would report it. As for the woman in Washtenaw County that died from West Nile virus, all we know is that she was between the ages of 75 and 85, and was a healthy, active individual. Her family has declined to be interviewed for a story.
Goober
Sun, Aug 26, 2012 : 11:29 p.m.
Nothing has changed. A lot of chicken little stuff recently. Part of life - people are born and people die. It is the way life is.
djacks24
Sun, Aug 26, 2012 : 8:58 p.m.
So does that mean the frequency of articles about West Nile will drop from two or three per week to once a week?
xmo
Sun, Aug 26, 2012 : 1:44 p.m.
Why all of the talk if the RISK is low? Does it sell advertising for NEWS.COM? " Public health experts maintain that the risk for exhibiting severe symptoms associated with West Nile is low."