Question

West Nile Virus: What Should We Do?

It is September 1, and Sean is beginning his infectious disease rotation in Regional Medical Center, a referral center for a large section of a Midwestern state. He hears that there are patients to see with suspected WNV in both the adult and child intensive care units. Sean’s attending physician tells him this is becoming a late summer ritual at Regional Medical Center.

Sean learns that these patients have gone into coma after experiencing a short period of fever, headache, and fatigue. Clinicians usually diagnose the disease using the newest antibody tests, but occasionally the test results are negative until late in the course of the disease. Alpha interferon therapy, a type of immune therapy, shows some evidence of benefit in animal models but is not approved by the FDA for use in WNV. Because alpha interferon has been FDA approved for other uses, however, clinicians occasionally use it “off label” when patients are not doing well. Often, all that clinicians can do to help the patients is provide support, frequently in intensive care, while the body either heals or deteriorates.

Sean goes to the research literature available on the Internet to learn more about WNV. Sean learns that WNV is spread by mosquitos, which bite infected birds and then bite humans. Mosquitos are more likely to bite birds with high levels of WNV in the summer and early fall, explaining the high incidence of WNV in humans in the same time period. Sean learns in his reading that birds, especially jays and crows, are particularly susceptible to WNV. In fact, public health officials have used testing of these species as a way to anticipate increased disease in humans.

The vast majority of those infected with WNV show no symptoms. About 20% experience fever, headaches, fatigue, and, occasionally, a reddish raised rash on the back, legs, or stomach and/or swollen lymph nodes. A small percentage of those with symptoms progress to experience central nervous system symptoms, which can include meningitis, encephalitis, and/or paralysis, potentially progressing to coma and possibly death. Over 90% of those with severe WNV survive, but a small percentage is left with brain damage. Based on hospital reports of severe WNV from hospitals like Regional Medical Center and recognizing that these reports are just the tip of the iceberg, the CDC estimates that 100,000 or more individuals in the United States may be infected with WNV in high-incidence years.

Severe WNV especially affects the very young and old, whose immune systems are most vulnerable to progression of the disease. HIV/AIDS patients and others with reduced immunity are also vulnerable to severe WNV. Person-to-person transmission has only been observed through blood transfusions and organ transplantation. There is now a vaccine for WNV approved for use in horses, given that horses often experience severe consequences of WNV. The vaccine is a DNA vaccine, which has not been approved for human use because of the theoretical possibility of altering the human DNA and causing cancer. Other vaccines, including those with live attenuated viruses, are under investigation.

Sean’s attending physician tells him that WNV was unknown in the United States before 1999. It may have mutated to be more easily transmitted to humans. The virus first appeared in New York and within 3 years had spread across the country. In epidemic years, associated with high volumes of mosquitos, thousands of patients have been hospitalized, and several hundred people have died from WNV.

Personal protection is provided by using mosquito repellant, avoiding dawn and dusk exposures (when mosquitos most often bite), and preventing stagnant pools of water in close proximity to humans. Community-wide mosquito spraying may have short-lived effects on the intensity of mosquito populations.

WNV drops dramatically after the first frost, which kills most of the disease-causing mosquitos. By extending the length of the frost-free period, global climate change has the potential to extend the West Nile “season” later into the fall.

We know a lot about WNV, Sean concludes, but there is a lot more we need to know, and a lot more we need to do.

Discussion Questions

1. What is the role of individual prevention in WNV?

2. What is the role of medical treatment in addressing the issues of WNV?

3. If an effective and safe vaccine was approved for WNV, who should receive the vaccine?

4. What population health measures do you recommend to control the spread of the disease?

5. What One Health concepts are illustrated by this case study?

Answer 1

West Nile Virus ( WNV)

West Nile virus is a A particular flavivirus, dangerous to humans. Flavivirus is any arbovirus of the Genus Flavivirus, many of which are transmitted by ticks or mosquitos.

1. Role of Individual Prevention in WNV

Preventing mosquito bites is the most effective way to prevent West Nile infection. To prevent mosquito bites an individual can do :

* wear long sleeved shirt and pants, when going outside, especially to farms and agricultural fields.

* Use insect repellents, that are recognized by EPA , Environmental Protection Agency.

* Do mosquito control measures in indoors by using nets and mesh for windows or other ventilations.

* Treat the clothes and accessories with permethrine

* Cover the baby carriers with nets

* Protect the environment from stagnant water, where mosquito lay eggs. Once a week empty the water holders, like buckets, plant pots and tyres etc.

While travelling overseas One has to take measures like;

- Choose appropriate lodging or hotels with Air conditioning.

- by bed net and carry it with you.

2.Medical treatment

Symptomatic treatment is the main measure for WNV infection:

Close monitoring is needed for the patient who has a risk of developing Increased Intracranial pressure and seizures as a result of Meningitis.

* Analgesics for pain and  Headache .

* Antiemetics for vomiting and nausea.

* Rehydration therapy for preventing Dehydration .

3. Vaccine for WNV

If a safe vaccine approved, then the following risk group have to take vaccines:

* people over the age of 50

* Farmers

* People with chronic medical condition like Diabetes, hypertension and cancer.

* People ,who stay in mosquito infested areas except pregnant ladies.

These category groups are more susceptible for WNV infection.

4. Population health measures

* Preventing mosquito bites by individual measures ( as described above)

Social measures: Mass disinfection in cities, towns and rural areas by spraying safe insecticides.

* Mass and individual Health education on Prevention of WNV infection

* Mass health education on Prevention of mosquito infestation and individual preventive measures.

* Encourage the public for early diagnosis and treatment of WNV infection.

* Appropriate health care delivery to rural areas also by Health authority and Government.

5. Health concept on Prevention of infectious disease WNV, its risk factors, process of vaccine development and its dangers are described in the case study.