In most situations, a simple blood test may be used to detect West Nile virus. This can detect whether you have West Nile virus-related genetic material or antibodies in your blood. If your symptoms are severe and connected to the brain, your doctor may prescribe a lumbar puncture. This is an invasive procedure that involves taking a sample of fluid from between the layers of the skull to check for viruses like West Nile virus.
Other tests include electron microscopy of tissue samples, PCR (polymerase chain reaction) testing of blood or tissue samples, and immunohistochemistry on biopsy specimens.
There is no specific treatment for West Nile virus infection. Your health care provider may recommend certain medications to reduce the risk of further complications if you have neurological problems due to West Nile virus. These may include anti-inflammatory drugs, such as corticosteroids, antiviral drugs, such as acyclovir (Zovirax) or famciclovir (Hivid), anticonvulsants, such as valproic acid (Depakote) or lamotrigine (Lamictal), or leukocyte adhesion inhibitors.
In some cases, patients may require intensive care because of worsening of existing conditions like diabetes or heart disease or because of development of new medical problems.
Tests for diagnosis Though numerous serological tests may be used to detect West Nile virus, the IgM capture ELISA is the most accurate test for clinically unwell horses. The IgM capture ELISA can confirm recent viral exposure. The IgM antibody increases swiftly after exposure but is only present for a brief time. Thus, detecting this antibody provides evidence of active infection. A negative result on an IgM capture ELISA does not rule out infection; a positive result does not indicate immunity either. To determine whether a horse has been infected with WNV, a blood sample should be taken approximately 14 days after the animal was exposed and then again at least once more during the next month.
Diagnosis can also be made using PCR testing of blood or brain samples. This method is very reliable for confirming infection but cannot distinguish past from present infection. It is important to note that although horses are susceptible to WNV infection, mortality rates are high enough that there is no need to cull healthy animals. Instead, protect vulnerable groups such as pregnant mares, young children, and elderly people who are at greater risk of serious illness if they are exposed to the virus.
Medical tests show that, like many other viruses, once infected with West Nile, a person acquires a natural immunity to subsequent infection by the virus for the rest of his or her life. This protection, however, may wane with time or in the presence of other health issues that weaken the immune system. There is no evidence that it will help your body fight off other infections during this period when the virus is present.
Those who have recovered from West Nile infection experience antibody-mediated immunity against further infection and illness. In fact, research studies have shown that up to 100% of people who recover from clinical infection develop protective antibodies which allow them to avoid future infections.
In addition, researchers have also found evidence suggesting that those who have had one exposure to the virus are less likely to contract it again compared to individuals who have never been exposed before. The likelihood of contracting the virus again depends on several factors such as age, prior exposure to other flaviviruses (such as dengue fever), and the strength of the immune response. Individuals who have never been exposed to West Nile but who have strong immune systems still tend to be protected against future exposures. However, those who have previously been exposed to the virus and whose immune responses were not strong enough to combat the first infection may be at risk for a severe outcome if they are exposed to the virus again.
Mild signs and symptoms of West Nile virus infection usually resolve on their own. Strong signs and symptoms, however, such as a severe headache, fever, disorientation, or abrupt weakness, necessitate emergency medical intervention. These symptoms are most often associated with older adults, but anyone can become ill. There is no evidence that suggests that children under the age of 18 cannot get West Nile virus.
West Nile virus disease remains endemic in many parts of the United States. Because infected mosquitoes transmit the virus to humans only during certain months of the year, the number of reported cases varies from year to year. However, because infection always results in symptoms, the number of undetected cases likely exceeds reported ones.
The virus was first identified in 1999 in New York City. Since then, increased incidence of West Nile virus has been observed throughout the United States. Although most people who are infected with West Nile virus do not develop serious illness, some develop mild flu-like symptoms after being bitten by an insect infected with West Nile virus. Others may experience more severe neurological problems including muscle weakness, paralysis, and death. Infection of pregnant women has resulted in births having low birth weights and premature infants. In addition, one in 150 infections leads to severe brain damage or death.
There is no treatment for West Nile virus infection.