Texas: First West Nile Case Of 2013

Photo Credit CDC 

 

#7319

 

 

Last year Texas endured a record-setting outbreak of West Nile Virus – spread by mosquitoes - recording 1869 cases and 89 death (see DVBID: 2012 Record Number Of West Nile Fatalities). While the entire country saw record numbers of WNV in 2012, roughly 1/3rd of all cases were diagnosed in Texas.

 

Nationwide, the numbers came in at:

 

Total cases                5,674 cases

Neuroinvasive cases   2,873 (51%)   

Mild cases                  2,801 (49%)

Deaths                          286

 

Neuroinvasive cases (which present with meningitis, encephalitis, or flaccid Paralysis) are severe enough that they result in hospitalization and diagnosis, and so they are considered the best indicator of the scope of each year’s epidemic.

 

Most people only end up with a mild, often sub-clinical infection, and never know they were infected. 

 

For every mild case diagnosed, there may be another 50 cases that go unreported.  

 

Yesterday the Texas Department of State Health Services released two statements on West Nile threat; one announcing their first diagnosed case of the year, and another warning that people need to start taking mosquito precautions now that summer is upon us.

 

 

 

Texas Confirms First West Nile Case of the Season

News Release
May 24, 2013

The Texas Department of State Health Services today confirmed the state’s first case of West Nile illness of the season. DSHS is urging people to take precautions to reduce the risk of contracting West Nile virus, a mosquito-borne illness.

 

West Nile illness was confirmed in an adult male from Anderson County. The patient is recovering from the neuroinvasive form of the disease. Additional details about the patient are not being released to protect the patient’s identity.

 

“This is a serious illness that can take a long-lasting toll,” said Dr. David Lakey, DSHS Commissioner. “Last season was unprecedented, with record numbers of cases and deaths reported in Texas. People need to do all they can to protect themselves from mosquito bites.”

 

Last year, Texas reported 1,868 human cases of West Nile illness, including 89 deaths.

 

State health officials said there is no way to predict the severity of this year’s season. The intensity of West Nile virus activity in Texas fluctuates from year to year and depends on a variety of factors including the weather, the numbers of birds and mosquitoes that maintain and spread the virus and human behavior. The season can last up until the first hard freeze of the year.

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DSHS Urges Precautions to Reduce West Nile Exposure

News Release
May 24, 2013

As Memorial Day approaches and people are spending more time outdoors, the Texas Department of State Health Services urges people to take precautions to reduce the risk of contracting West Nile virus, a mosquito-borne illness.

 

Last year, Texas reported 1,868 human cases of West Nile illness, including 89 deaths. State health officials said there is no way to predict the severity of this year’s season. The intensity of West Nile virus activity in Texas fluctuates from year to year and depends on a variety of factors including the weather, the numbers of birds and mosquitoes that maintain and spread the virus and human behavior. The season can last up until the first hard freeze of the year.

To reduce exposure to West Nile virus:

• Use an approved insect repellent every time you go outside and follow the instructions on the label. Among the EPA-approved repellents are those that contain DEET, picaridin, IR3535 or oil of lemon eucalyptus.
• Regularly drain standing water, including water collecting in empty cans, tires, buckets, clogged rain gutters and saucers under potted plants. Mosquitoes that spread WNV breed in stagnant water.
• Wear long sleeves and pants at dawn and dusk when mosquitoes are most active.
• Use air conditioning or make sure there are screens on all doors and windows to keep mosquitoes from entering the home.

Symptoms of the milder form of illness, West Nile fever, can include headache, fever, muscle and joint aches, nausea and fatigue. People with West Nile fever typically recover on their own, although symptoms may last for several weeks. Symptoms of the more serious form, West Nile neuroinvasive disease, can include those of West Nile fever plus neck stiffness, stupor, disorientation, tremors, convulsions, muscle weakness and paralysis. Up to 80 percent of people infected with the virus will have no symptoms.

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Given its severity (and that of less common mosquito borne diseases in the U.S., like EEE, Dengue, SLEV), it makes sense to take steps to protect yourself and your family.

 

So today would be a good day to go around and look for likely breeding places in, and around your home. This should become a weekly habit – at least during mosquito season.

 

And to help you with warding off these pests, we’ve an interactive insect repellant search engine developed by the EPA that will that will allow you to input your needs and it will spit out the best repellants to use.

 

(click image to go to search engine)

MMWR: Arboviral Disease Surveillance – 2010

 

 

# 5738

 

 

Arboviruses belong to a large group of viruses carried and transmitted by biting mosquitoes, ticks, and other arthropods when they take a blood meal from susceptible vertebrate hosts.

 

The map below shows the global distribution of some of the more common encephalitis producing arboviruses.

 

 

A few of my blogs from last year on these viral threats included:

 

EEE Reports In Michigan And R.I.

Florida Records 4th EEE Death In July

ASTMH: Dengue and Insect-Borne EIDs In The US

Eastern Equine Encephalitis (EEE)

 

This week the CDC’s MMWR contains a surveillance report on arthropod-borne viruses – or arboviral - infections (excluding Dengue which is tracked separately) in the United States during 2010.

 

And last year, it turns out, was a banner year for arboviral disease in the United States, with the number of West Nile Virus (WNV) cases (1,021) up sharply over 2009, and 62% of those producing neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis).

 

Other viral players included California serogroup viruses (CALV), eastern equine encephalitis virus (EEEV),  St. Louis encephalitis virus (SLEV) and Powassan virus (POWV).

 

 

A few excerpts from the report follow (slightly reformatted for readability). Follow the link to read it in its entirety.

 

West Nile Virus Disease and Other Arboviral Diseases --- United States, 2010

Weekly

August 5, 2011 / 60(30);1009-1013

Arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. Since West Nile virus (WNV) was first detected in the Western Hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the United States (1).

 

However, several other arboviruses continue to cause sporadic cases and seasonal outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis) (1,2).

 

This report summarizes surveillance data reported to CDC in 2010 for WNV and other nationally notifiable arboviruses (excluding dengue, which is reported separately).

 

In 2010, 40 states and the District of Columbia (DC) reported 1,021 cases of WNV disease. Of these, 629 (62%) were classified as WNV neuroinvasive disease, for a national incidence of 0.20 per 100,000 population. States with the highest incidence were Arizona (1.60), New Mexico (1.03), Nebraska (0.55), and Colorado (0.51).

 

After WNV, the next most commonly reported cause of neuroinvasive arboviral disease was California serogroup viruses (CALV), with 68 cases, followed by eastern equine encephalitis virus (EEEV), 10 cases, St. Louis encephalitis virus (SLEV), eight cases, and Powassan virus (POWV), eight cases. WNV and other arboviruses continue to cause focal outbreaks and severe illness in substantial numbers of persons in the United States. Maintaining surveillance remains important to guide arboviral disease prevention activities.

 

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Given the limitations of surveillance, and the fact that many people experience mild, or non-specific symptoms of infection, the true burden of these (mostly) mosquito borne viruses in the United States can only be estimated.

 

The editorial note to this report states:

 

Detection and reporting are incomplete, leading to a substantial underestimate of the actual number of cases. Based on previous studies, for every case of WNV neuroinvasive disease, approximately 140 human WNV infections occur, with 80% of infected persons remaining asymptomatic and 20% developing nonneuroinvasive disease (7,8).

Extrapolating from the 629 reported WNV neuroinvasive disease cases, an estimated 88,000 infections and 17,600 cases of nonneuroinvasive disease might have occurred in 2010; however, only 392 (2%) nonneuroinvasive disease cases were reported.

 

 

As the chart below indicates, the older adults are more apt to develop neuroinvasive disease from a WNV infection.

FIGURE. Incidence* of cases (N = 629) of West Nile virus neuroinvasive disease,† by age group --- United States, 2010

* Per 100,000 population, based on July 1, 2010, U.S. Census estimates.

† Meningitis, encephalitis, or acute flaccid paralysis.

 

 

A summation of the report reads:

What is already known on this topic?

Since West Nile virus (WNV) was first detected in the Western Hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the United States. However, several other arboviruses can cause sporadic cases and seasonal outbreaks of neuroinvasive disease.

What is added by this report?

WNV was the most common cause of neuroinvasive arboviral diseases in the United States in 2010; however, La Crosse virus was the most common cause among children. Eastern equine encephalitis, although rare, remained the most severe arboviral disease, with a 50% case-fatality rate.

What are the implications for public health practice?

WNV and other arboviruses continue to be a source of severe illness each year for substantial numbers of persons in the United States. Maintaining surveillance remains important to help direct and promote prevention activities.

 

 

While the odds of contracting a serious illness from mosquito bites in the United States remains very low - if you visit or live in mosquito territory – it is worth remembering Florida Department of Health’s, (FDOH)
recommendation that individuals protect themselves by following the “5 D’s”.

Eastern Equine Encephalitis (EEE)

 

 

# 4741

 

 

Yesterday the local news carried word of the death of an adult female in Hillsborough County (ie. Tampa region), Florida from mosquito borne EEE (Eastern Equine Encephalitis).

 

EEE (Triple `E’) is an often serious, but exceedingly rare illness in humans.  It is one of more than 100 kinds of arbovirus (viruses transmitted by arthropods  e.g., Mosquitoes, sandflies, midges, or ticks).

 

According to the MMWR  (here), between 1999 and 2008 there were a median of seven (range: 3--21) EEE cases (not deaths) reported in the United States each year.

 

In addition to EEE, West Nile virus (WNV), La Crosse virus (LACV), and St. Louis encephalitis virus (SLEV) also circulate at low levels in the United States.

 

 

While of concern, to keep things in perspective, on average 58 people are struck and killed by lightning each year in the United States, and Bee stings account for an additional 40 deaths each year.

 

Which isn’t to minimize EEE or any of the other arboviruses, or to suggest that people not take precautions against mosquitoes, but is simply a reminder that a lot of the diseases we talk about in this column are pretty rare.

 

In recent weeks, Dengue has become a big story here in Florida, but once again, we’re talking a couple of dozen confirmed cases out of a population of 18 million.

 

The actual incidence of Dengue is probably much higher, but as with most viruses, many cases are sub-clinical or asymptomatic and are therefore never diagnosed.  

 

First, the story about the EEE fatality, then a bit of discussion about the way this rare virus makes its way into the human population.

 

First human EEE death confirmed in Hillsborough County

State's first encephalitis death in two years

Updated: Wednesday, 21 Jul 2010, 6:18 AM EDT
 

MyFoxTampaBay.com staff report

TAMPA - Health officials in Hillsborough County have confirmed the first human death this year from Eastern Equine Encephalitis.

 

A woman living in the northern part of the county died July 1, the county health department said, and it is believed that she had other health issues as well.

 

This is the first human death from EEE in the state of Florida since 2008.

 

Four horses in the county have also tested positive for the disease in the last several weeks, according to the health department. Officials say finding the disease in animals means that the likelihood of humans becoming infected increases.

 

Hillsborough County Mosquito Control will be spraying pesticides over much of the county Wednesday morning.

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While the number of yearly cases is low, the distribution of EEE in the United States far ranging.

 

 

The natural host for the EEE virus are songbirds, which can become infected generally without suffering ill effect.  The virus is spread among these birds by the blood feeding of female mosquitoes (males don’t bite).

 

After an infected mosquito feeds on a bird, the bird becomes infected and the virus begins reproducing. After a few days, and for only a few days, the bird’s bloodstream contains enough virus to infect subsequent mosquitoes that feed on it.

 

Culiseta melanura, which means "curly black hairs", is the species of swamp mosquito that serves as the primary vector for this virus among birds.

 

It, however, isn’t usually attracted to bite humans.

 

So it generally requires a secondary type of mosquito - one that isn’t quite as picky a feeder - such as the Aedes albopictus or  Coquillettidia perturbans  `salt and pepper’ mosquito, to bite an infected bird in order to move it into the equine or human population.

 

Humans and horses don’t develop a high enough viral EEE titer in their bloodstream to pass on the virus if they are subsequently bitten by a mosquito, so they are considered a `dead-end host’.

 

For more on this fascinating topic, I’ve found an absolutely terrific multimedia presentation on arboviruses in Florida.

 

It is a narrated slide show, by Rebecca Shultz, the Arthropod-borne Disease Surveillance Coordinator for the Florida Department of Health, and it covers EEE, SLEV, and West Nile Virus.

 

The presentation runs just over 20 minutes.   The transcript is here.  Click the image below (or this link )to go to the slide show, and turn on your speakers.

 

Highly recommended.

 

 

As the Miami-Dade County Health Department reminds us, to protect yourself from mosquitoes, you should practice the “5 D's”:

• Dusk and Dawn – avoid being outdoors when mosquitoes are very active 
  
• Dress – wear clothing that covers most of your skin 
  
• DEET – repellents containing up to 30 percent DEET (N, N-diethyl-meta-toluamide) are recommended. Other effective mosquito repellents include picaridin, oil of lemon eucalyptus, and IR 3535. Always read label directions for approved usage before your apply a repellent. Some repellents are not suitable for children. 
  
• Drainage – check around your home to remove standing water, where mosquitoes may lay eggs.

 

As long as you observe these simple precautions (and this isn’t just advice for Floridians), you can reduce your (already slight) risk of being infected by any of these mosquito borne illnesses.

 

For those who would like to follow Florida’s surveillance program for arboviruses, weekly reports are available from the Florida Department of Health.

 

Weekly Data for Arbovirus Surveillance