Mosquitoes are no stranger to our country. But did you know that some mosquitoes can also transmit dangerous diseases? Today we are going to talk about a rare but potentially dangerous disease transmitted by mosquitoes. That is the St. Louis Encephalitis Virus, or SLEV for short.
What is St. Louis Encephalitis Virus (SLEV)? How is it spread?
Simply put, this is a virus that is spread by mosquitoes. It is transmitted specifically by the Culex mosquito. When this virus enters your body, the most dangerous thing is that it can cause swelling inside the brain, which is inflammation. In medical terms, we call this encephalitis.
Most people get SLEV from being bitten by an infected mosquito. However, it is not spread from person to person by shaking hands, hugging, drinking from the same glass, or kissing. That's a big relief, isn't it? However, very rarely, it can be spread through blood transfusion .
Where is this disease most common? Is it common?
This disease, called SLEV, is not very common. Most cases are reported from the United States, especially the eastern, central, and southwestern states. However, these patients have also been reported from countries such as Argentina, Canada, the Caribbean, and Mexico.
According to the US Centers for Disease Control and Prevention (CDC), only a little over 300 cases of SLEV have been reported between 2003 and 2024. In the US, the disease usually occurs during the warm season, from June to October. However, in warmer climates, it can occur year-round.
What are these SLEV symptoms?
The symptoms of SLEV vary. Sometimes you may not have any symptoms at all, or you may have symptoms that resemble a common cold.
Mild symptoms
These are the mild symptoms that are commonly seen:
- Feeling extremely tired (fatigue)
- Fever
- Headache
- Muscle weakness
- Nausea
Severe symptoms
However, if SLEV becomes severe, it can cause swelling of the brain, which is what we mentioned earlier, encephalitis. The symptoms are a bit more dangerous:
- Changes to your mental function, such as confusion, agitation, and disorientation
- Stiff neck
- Uncontrollable shaking of the limbs (tremors)
If you or someone you know shows signs of loss of consciousness, you should go to a hospital emergency room as soon as possible. It's very important!
In severe cases of SLEV, coma and even death can occur.
How long does it take for symptoms to appear?
It usually takes four to fourteen days for SLEV symptoms to appear after an infected mosquito bites you. We call this the incubation period, or simply the time before symptoms appear.
How does St. Louis encephalitis develop?
Mosquitoes get SLEV by sucking blood from infected birds. Then, when these infected mosquitoes bite your skin, that is, when they suck blood, the SLEV virus enters your body. Importantly, humans are considered the 'dead-end host' for this virus. Do you know why? You don't have high levels of the virus in your blood, so you can't spread the disease to anyone else. If someone gets SLEV, they don't need to self-isolate, wear a mask, or disinfect their homes.
But as we said before, very rarely, this infection can be spread through a blood transfusion.
Who is at higher risk of developing this?
St. Louis encephalitis virus is a very rare disease, but you may be at higher risk of contracting SLEV if you:
- If you live or work in areas where SLEV is endemic, especially near areas where mosquitoes breed, such as water bodies, swamps, or forested areas.
- If you spend a lot of time outdoors in areas with an epidemic situation, especially in the morning and evening, because that's when mosquitoes are most active.
Who is more likely to develop severe SLEV symptoms?
You are more likely to develop severe SLEV symptoms if these factors apply to you:
- If you are over 50 years old.
- If your immune system is weak.
- If you have diabetes .
What are the possible complications of St. Louis encephalitis virus?
Even with successful treatment, SLEV can cause some long-term complications. This means that some problems may remain even after the disease has resolved. For example:
- Changes in your behavior. This includes things like being easily angered, anxiety, depression, and irritability.
- Difficulty walking.
- Difficulty remembering things (memory loss).
- Also, SLEV can cause intellectual disability in young children .
How do doctors diagnose the St. Louis encephalitis virus?
A doctor will first ask about your medical history, symptoms, and perform a physical exam. They may then ask questions like these:
- Have you traveled anywhere recently?
- Have you been bitten by mosquitoes recently?
- When did the mosquitoes bite?
- When did you first notice the symptoms?
If your doctor suspects that you have SLEV, he or she will order a blood test. This is called a serological test. This looks for antibodies in your blood, specifically an antibody called Immunoglobulin M (IgM). Your immune system makes these antibodies to protect you from infection. These antibodies are also produced against SLEV infection.
Sometimes doctors may recommend taking a sample of your spinal fluid (spinal tap / lumbar puncture) to check for IgM antibodies in the cerebrospinal fluid (CSF).
How is SLEV treated?
There is no specific treatment for St. Louis encephalitis virus. However, if you have mild symptoms, your doctor may recommend the following:
- For headaches, take painkillers such as acetaminophen (e.g. Tylenol®), aspirin (e.g. Bayer®, Bufferin®), ibuprofen (e.g. Advil®, Motrin IB®), or naproxen sodium (e.g. Aleve®).
- Drinking plenty of fluids, especially water, is a good way to prevent dehydration.
- Medicines for nausea and vomiting. Examples include bismuth subsalicylate (e.g. Pepto-Bismol®) and phosphorated carbohydrate solution (e.g. Emetrol®).
But if you have severe symptoms, you may need to be hospitalized and monitored. If SLEV causes severe inflammation in your brain, a surgeon may need to remove part of your skull (craniotomy) to relieve the pressure on your brain.
Can SLEV be cured with antiviral drugs?
No, antiviral drugs cannot cure SLEV. Mild symptoms can be relieved with over-the-counter medications.
Is there a vaccine for SLEV?
No, no vaccine has yet been found to protect against SLEV.
How long does it take to heal?
The time it takes for you to recover depends on the severity of the infection. In mild cases, your symptoms may go away in a few weeks. However, some symptoms may take several months to completely go away.
When should I see a doctor?
If you develop symptoms of St. Louis encephalitis virus, especially if you have recently been bitten by a mosquito, see a doctor immediately. A doctor can evaluate your symptoms, perform any necessary tests, and recommend treatment.
You can also ask the doctor questions like:
- Are my symptoms serious?
- Will I have to be hospitalized?
- When will I start feeling better?
- How can I manage my symptoms at home?
- Are there any serious symptoms I should be aware of?
- Do I need to come back for a follow-up appointment?
What can I expect if I have this condition?
Most people who get St. Louis encephalitis virus have no symptoms, or their symptoms are very mild. You may recover before the virus causes inflammation in your brain. However, it can be life-threatening, especially if you are over 50, have diabetes, or have a compromised immune system. If you have symptoms, see a doctor for advice. He or she will tell you what to expect.
What is the mortality rate for St. Louis encephalitis?
The mortality rate for people who develop SLEV is between 5 and 20 out of 100. This rate is higher if you are over 50 years old or have high blood pressure (hypertension).
Can St. Louis encephalitis virus be prevented?
As we have already said, there is no vaccine to prevent St. Louis encephalitis virus. The best way to protect yourself from SLEV is to avoid mosquitoes. You can do the following to protect yourself from mosquitoes:
- Avoid traveling to areas where SLEV is endemic.
- Avoiding stagnant water, such as ponds and swamps. Also, always emptying water from birdbaths, buckets, watering cans, and garbage cans. This is because mosquitoes breed in stagnant water.
- Installing tight-fitting screens on the windows and doors of your home.
- Using insect repellant when going outside.
- When spending time outdoors, wear thick, long-sleeved shirts, pants, and socks.
Why is this called St. Louis encephalitis?
This disease is called St. Louis encephalitis because the virus was first identified in 1933 in the city of St. Louis, Missouri, USA. During that time, more than 1,000 cases were reported.
Can I donate blood if I have a St. Louis encephalitis virus infection?
No, you cannot donate blood if you have an active SLEV infection. However, you should be able to donate blood about four months after the infection has cleared. Before donating blood, be sure to tell a doctor if you have recently had a SLEV infection.
Most of the time, mosquitoes are just annoying. But sometimes they can carry diseases, and when they bite you, they can pass them on to you. St. Louis encephalitis virus is one such disease. For most people, the risk of getting seriously ill from it is low. But severe, sometimes life-threatening, symptoms can occur. The best way to protect yourself is to avoid mosquitoes, especially in areas where SLEV is common. If you have been bitten by a mosquito and develop symptoms of SLEV, see a doctor. He or she can treat your symptoms and, if necessary, monitor you to make sure they don’t get worse.
The most important things to remember in this article
St. Louis encephalitis virus (SLEV) is a mosquito-borne disease that can cause swelling of the brain (encephalitis). It is not usually transmitted from person to person.
- Symptoms can range from mild (fever, headache) to severe (confusion, stiff neck). If you experience severe symptoms, go to the hospital immediately.
- There is no specific medicine or vaccine for this. Treatment is for the symptoms.
- The most important thing is to protect yourself from mosquitoes. Do things like remove dirty water, use mosquito repellent, and wear clothing that covers your body.
- If you are over 50, have a weakened immune system, or have diabetes, you are at higher risk of developing a serious condition.
- If you have any doubts or symptoms, never delay seeking medical advice.
` St. Louis Encephalitis, SLEV, Mosquitoes, Virus, Brain Inflammation, Encephalitis, Symptoms, Prevention
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