Clinical Presentation of West Nile Virus

Clinical Presentation

What are the clinical signs of West Nile virus infection?

The clinical signs of WNV infection vary between species; however, WNV does not always produce illness in animals or people.  Clinical signs according to species are outlined below:

• Dogs and Cats
• Although it is possible for dogs and cats to be exposed to West Nile Virus, the virus does not tend to cause serious illness in these animals.

• Birds – West Nile virus has been reported in more than 150 species of North American birds 

• Illness in birds includes three phases, although birds do not usually show signs of infection until the last stage of the disease:
• Phase I signs include depression, anorexia and drowsy appearance; recovery is likely
• Phase II signs include depression, anorexia, drowsy, greenish diarrhea, central blindness and ataxia; recovery possible with intense therapy
• Phase III signs include seizures, tremors and death 

• Horses – the virus infects the central nervous system and may cause symptoms of encephalitis 

• Muscle fasciculations
• Mentation/behavior changes
• Lethargy
• Loss of appetite
• Weakness (especially of hind limbs) 

• Ataxia
• Paralysis (especially of hind limbs)
• Convulsions
• Circling
• Head pressing 

• Humans
  
• Asymptomatic disease
• Most people infected (approximately four out of five) have no symptoms
• West Nile fever (seen in about 20% of human cases)
• Fever
• Headache
• Tiredness
• Body aches
• Skin rash on trunk of body
• Swollen lymph glands
• Severe disease (Neuroinvasive disease, West Nile encephalitis, meningitis or West Nile poliomyelitis) is seen in about 1 of every 150 human cases

• Headache
• High fever
• Neck stiffness
• Stupor
• Disorientation
• Coma
• Tremors
• Convulsions
• Muscle weakness
• Paralysis

What can you do to prevent West Nile Virus?

A Case of West Nile Encephalitis in a Human:

This author was given a rare opportunity to interview a young woman in Guilford County, N.C. who became infected with West Nile virus in 2007.  Here is her story in her own words:

In July 2007, when I was 17 years old, I traveled to Costa Rica to participate in a tropical ecology course.  I stayed there for three weeks, mostly in the rainforest.  Needless to say, I received a lot mosquito bites during that time.  During the return trip home, I was feeling tired and run down, like I was getting the flu.  The day after I returned home, I developed a high fever, nausea, vomiting, joint pain and really bad headaches.  I was in bed for about five days and was incredibly weak; I felt like I had a brain fog – I couldn’t concentrate and was having trouble remembering things.  By about the fifth day, my fever had reached nearly 105 degrees and my mother took me to the emergency room at the hospital.  I was having violent chills, hallucinations and I was dehydrated and so weak and my head hurt badly.  I was given IV fluids and anti-inflammatories and they ran a bunch of tests.  My fever came down and they let me go home.  

I continued to have some nausea and vomiting for about two more days, and weakness, terrible joint pain and that “brain fog” for about two more weeks.  I had followed up with my regular doctor shortly after my ER visit and he drew more blood for testing.  After about two more weeks passed, I began feeling better.  Around the same time I was feeling better, my doctor called and said, “You have West Nile virus.”  

The end result of my infection with this virus is that I was not allowed to give blood for five years, which was okay with me because I developed a terrible phobia of needles.  I think the phobia comes from the hallucinations I was having in the emergency room coupled with the multiple needle sticks I had to endure since I was so dehydrated and they had such a hard time finding a vein.  I still have occasional random joint pains, which may be related to the viral infection.   T.S.

Thank you to “T.S.” for sharing her story with me.  I have first-hand knowledge that she suffered cruelly when she was ill with West Nile virus.  She is now 23 years old and employed as an Environmental Specialist with the North Carolina Department of Environment and Natural Resources. 

References: 

Centers for Disease Control and Prevention, (2012). West nile virus; Symptoms of west nile virus. Retrieved from website: http://www.cdc.gov.

Subbiah, E. Equine Viruses Class Notes.  VM8124. 2013.

Pennsylvania’s West Nile Virus Control Program, (2013). What horse owners should know about west nile virus.  Retrieved from website:  http://www.westnile.state.pa.us/animals/horses.htm.

West Nile Virus, (2012). West nile virus symptoms in birds. Retrieved from website: http://www.west-nile-virus-prevention.com/article-west-nile-virus-birds.html.

Images:  

http://www.countrysidemag.com/issues/96/96-1/west_nile_virus_in_horses.html

http://www.cdc.gov

http://www.blogs.equisearch.com

http://wobm.com/west-nile-virus-found-in-three-more-birds/

http://stayhealthla.org

http://www.vdh.state.va.us