West Nile Virus May Give Permanent Symptoms
West Nile Virus is mainly a mosquito borne virus that mainly infects birds but also affects other animals including humans and other mammals. West Nile virus appeared in the US in 1999 with viral encephalitis reported in humans and horses. In 2007, the number of human West Nile cases reported was 3,623 and the number of deaths was 124 which is a decrease from 2006. West Nile Virus has three different possible stages in humans–not everyone progresses from the asymptomatic mild infection to the more serious phases. The first phase of infection is an asymptomatic phase of infection; the second phase is a mild febrile syndrome termed West Nile Fever. The third phase of West Nile infection is a neurologically invasive disease termed West Nile meningitis or encephalitis. In infected individuals the ratio between the development of each phase is roughly 150 patients in phase 1(asymptomatic): 30 patients in phase 2 (mild febrile illness): 1 patient in phase 3 (severe neurological illness). The more serious encephalitis is characterized by mild initial symptoms but also a decreased level of consciousness, which may approach a coma-like state. There are also extra pyramidal (involuntary movements) disorders. Recovery may be marked by a long convalescence phase with remarkable fatigue. More recent outbreaks have allowed a more in depth study of the disease and additional, rarer, outcomes have been identified. For example, the spinal cord may be infected.
One in 150 people infected with West Nile virus can develop severe neurological disease. As many as 40% of the severely ill patients can develop serious symptoms for the remainder of their lives according to Kristy Murray, PhD, DVM, University of Texas Health Science Center in Houston, Texas.
These results are from five years of data on 108 Houston residents who had severe West Nile Virus disease after infection with the mosquito-borne virus. Murray’s team evaluated the patients every six months.
60% of the severely ill patients still had serious symptoms as much as a year after their West Nile virus infection. Up to five years later, 42% of the severely ill patients still had not completely recovered.
The long lasting symptoms were numerous and included fatigue, difficulty with walking, memory problems, muscle weakness, depression, and personality changes.
This doesn’t happen to the vast majority of people who get bitten by a mosquito carrying West Nile virus.
80 percent of patients who were infected with West Nile virus develop no symptoms — most don’t even know they are infected, according to Dr. Murray. 20% have only a mild, flu-like illness with no problems in terms of recovery. A very small number of West Nile patients will develop the more severe neurological disease.
Patients over age 50 years old are more likely than young people to get severe West Nile disease. The average patient in Dr. Murray’s study was 52 years old however they also saw severe disease in some children, too. One child was only six months old; another child was 11 years old.
Severe West Nile disease can include a high fever leading to hospitalization. It can also cause meningitis, encephalitis, and even a polio-like paralysis. West Nile meningitis attacks the protective membranes covering the brain and spinal cord. West Nile encephalitis is an even more serious infection of the brain tissue. Dr. Murray and her colleagues discovered that 60% of the seriously infected patients with West Nile encephalitis still are likely to have symptoms after five years.
A disturbing finding is that 31% of people with serious West Nile disease developed clinical depression. Another disturbing discovery was that 25% of patients developed personality changes. Many patients became more irritable and angry. The families reported that patients had a short fuse, easily lost their tempers. Many patients also had difficulty walking normally. Other neurological problems included a loss of muscle strength, hearing problems, sensory loss, and muscle tremors.
The bottom line is to protect yourself from West Nile Infection and then you won’t have to worry about these serious complications–which are rare but frightening.
Protecting Yourself Against West Nile Virus (from FDA and CDC)
For people living in areas where West Nile virus is active, the Centers for Disease Control and Prevention recommends the following:
- When going outdoors, apply insect repellant containing DEET to bare skin and clothing. Mosquitoes may bite through thin clothing. Products containing 10 percent or less DEET are the most appropriate for children aged 2-12 years. Always follow product instructions when using repellent. (Ultrasonic devices are not effective in preventing mosquito bites.)
- Wear loose-fitting clothing that covers legs and arms while in areas where mosquitoes are likely to be present.
- To the extent possible, avoid outdoor activities between dusk and dawn, when mosquito activity is greatest.
- Ensure that window and door screens are in good repair and that other routes of mosquito access to buildings and living space are blocked.
- Clean out clogged rain gutters to avoid collecting water where mosquitoes can lay eggs.
- At least once or twice a week, empty water from flowerpots, pet food and water dishes, birdbaths, swimming pool covers, and other items that collect water.
Dr. Murray reported these findings at the 2008 International Conference on Emerging Infectious Diseases, (March 6-19 in Atlanta).
