Signs and Symptoms of WNV

There are bio-markers that will let you and healthcare staff know that something is not going well in the body. These will be outside of typical norms that are seen in healthy demographics. These are called "signs". The "symptoms" are what you are feeling, and experiencing that are not tangible for a healthcare provider to measure. When we combine these signs and symptoms, we can effectively hone in on an issue that could be the culprit for your sickness. West Nile Virus is no different, in that it has a characteristic set of signs and symptoms that are indicative of what system of the body is affected. With WNV, it is the neurological system that is receiving the brunt of the issues. So lets see the normal signs and symptoms:

Early WNV - Fever
                    - Headache
                    - Body Aches
                    - Fatigue
                    - Back Pain
                    - Skin Rash (occasional)
                    - Swollen lymph nodes (occasional)
                    - Eye pain (occasional)

If the disease is left unchecked or treated improperly, it can and often times will progress to an infection with worsening symptoms. These become more severe, systemic in nature, and possibly life threatening. They include:

Late or indicative of an infection
                    - High fever
                    - Severe headache
                    - Stiff neck
                    - Disorientation/confusion
                    - Stupor/coma
                    - Tremors or muscle jerking
                    - Lack of coordination
                    - Convulsions
                    - Pain
                    - Partial paralysis or weakness

           Fig. 1 Signs and Symptoms 

            Photo Credit

This figure is an easy reference to be able to visualize when things progress from bad to worse. If left untreated, or treated improperly, the disease will progress to a full blown systemic infection in which death is quite possible. So when any of these signs and symptoms are present, especially together in a group, it is time to immediately contact your physician or seek help.

References:

The Mayo Clinic. (2012). Disease and conditions: West Nile virus.
Retrieved from http://www.mayoclinic.org/diseases-conditions/west-nile-virus/basics/symptoms/con-20023076

Being Diagnosed, How They Know.

You have been getting very frequent and intense headaches recently. You are coming down with a fever and think its a good time to visit your physician. You've called, made an appointment, and by the time you go, you feel much worse.

Your doctor is going to immediately start putting together the puzzle of symptoms, signs, history, and any other pertinent key factors.

Most cerebral viral maladies all have similar symptoms, such as encephalitis. So the ways of determining what is causing these handful of symptoms, is similar. It is called a lumbar puncture to test the cerebrospinal fluid. This is done with a sizable needle and isn't usually a fun procedure.

Fig. 1: Lumbar Puncture

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You have sat through it though, and they are now looking at your test results. What they were looking for were antibodies, or proteins our bodies produce after being exposed to a pathogen. These antibodies are specific to diseases, and for West Nile Virus, they know exactly what to look for. This is an "IgM" antibody that is specifically produced against the WNV antigen. After IgM antibodies are made, then IgG antibodies, which are long term are produced. So if a lab test is performed and only IgG antibodies (long term) are found, this is only evidence of previous infection from WNV, not a current episode of it, as that would produce IgM specific antibodies.

Fig. 2: West Nile Virus, Antibody, and Vector

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There are other tests, such as polymerase chain reaction, that are tested against CSF, blood and tissue samples early on in the disease. Currently though, the antibody test from cerebrospinal fluid is the fastest, most accurate, and best at determining between current and past infection.

Your doctor calls you after the lab results come back. He has bad news, but its good as its treatable. He lets you know you have a positive antibody test for a current West Nile Virus infection and will be treating you accordingly to reduce your symptoms and help with your wellness. We will discuss what those treatments are in future blog posts.

References:
Barzon, L., Pacenti, M., Ulbert, S., & Palu, G. (2015). Latest developments and challenges in the diagnosis of human West Nile virus infection. Expert Review of Anti Infective Therapy, March 2015

 

Etiology and Pathophyisiology: the How

Let's talk about what West Nile does once it is in your body. So we know its coming from a "vector", or a mosquito in this case. This mosquito is carrying the virus and once it bites you this virus goes from it, to you. The mosquito acquired the disease by feeding on the blood of a bird, making it a temporary transport vessel until it gets to another bird, animal, or human. Now lets dispel a myth that you can transfer the disease to others by shaking hands or kissing. This is FALSE, and can not occur.

So, back to you being bitten.......



Photo Credz:

Now the virus is in your body, lets discuss what happens and the effects and consequences of this transfer. Once bitten, the virus usually replicates at the site of injection from the mosquito's mouth parts. Here, after sufficient replication of the virus it will travel via the blood stream and lymph system until it reaches its intended location.

The virus passes gate like receptors that are mediated by tumor factor alpha, until the brain and spinal cord are reached. Here, the virus directly invades and infects neurons, especially those that are deep to the grey matter. The infection of these neurons, and those surrounding those that are now impaired, are what contribute to the signs and symptoms of the disease. The paralysis, encephalopathy, seizures, headaches, and other neural disturbances are a direct output of infected and disabled neurons. It is at this point that a healthy immune system will eventually recover and shake off this viral infection. It will take a little time, and it won't be comfortable, but there is a very high survival rate. Now onto those who are more at risk........

Photo Credit

As for lending factors that increase morbidity or mortality, it is mainly age and health status. Through pre-mentioned studies, those over the age of 50 are at a greater risk for serious infection, and then a greater risk of a fatal infection. Those with weakened immune systems, incapable of fighting of a viral disease load are also at risk, despite their age. This includes recent organ transplant recipients who are on medications to weaken the immune system. Other than these two factors, time of year, physical location, and amount of time spent outside (all related to mosquito bites) are directly correlated to getting the infection.

References:
Samuel, M., & Diamond, M. (2006, October 1). Pathogenesis of West Nile Virus Infection: A Balance between Virulence, Innate and Adaptive Immunity, and Viral Evasion. Retrieved April 12, 2015, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1617273/

Virology, Pathology, and Clinical Manifestations of West Nile Virus Disease - Volume 11, Number 8-August 2005 - Emerging Infectious Disease journal - CDC. (n.d.). Retrieved April 12, 2015, from http://wwwnc.cdc.gov/eid/article/11/8/05-0289b_article

Epidemiology of WNV

With West Nile Virus originating in African tropics and sub-tropics, it was first documented in the United States in New York City in 1999. Since then, it has seen an explosion, expansion, and then a relative normalization. Initially this spread away from New York in a  general spread out fashion among the south, east, and west. Then there was a massive convergence of incidence in the Midwest to the East face of the Rocky Mountains. This eventually normalized again with a more even spread nationwide, with just a slight higher incidence in the west.

West Nile Virus does not seem to affect any age range more prevalently than others. There is an even age distribution with the median age being 49. There is a higher risk of neuroinvasive WNV and death associated with an increase in age. The median age range for all other neuroinvasive diseases is 69 years of age. This is a sharp increase from the 49 years of age seen with WNV.

The transmission is seen as generally seasonal for the more temperate areas of the United States. here, the majority of cases are seen in late spring, and summer. If we shift our view to further south to more humid and tropical climates (more conducive to mosquito populations) we see the season as a much wider swath. There are cases reported as late in the year as December, and as early as April the next year.

 

 

Fig 1. 2014 West Nile Virus Epidemiology Map

As for mortality, there is approximately a 10% fatality rate among properly reported and diagnosed WNV cases. This is seen as higher in the elder population, as is common with most neuroinvasive diseases. It is rarely reported as fatal in children, but there have been a handful of sporadic cases.

Today, we are still currently seeing the bulk of the cases in the west, such as California, the southern states, and northern Midwest states such as North and South Dakota. Other than these areas there is a lesser, but still even spread. The only areas that aren't showing any WNV at all, or are only showing non-human WNV are in the upper extremes of the Northeast. Here in Maine and surrounding states we see a relative disease free region. This is undoubtedly due to the inability for the main vector (mosquitos) to survive in such a year round temperate climate.

Search Terms: West Nile Virus on Centers for Disease Control and Prevention

References:

West Nile Virus. (2015, January 30). Retrieved April 6, 2015, from http://www.cdc.gov/westnile/

West Nile Virus. (2011, July 1). Retrieved April 6, 2015, from http://who.int/mediacentre/factsheets/fs354/en/