A seven-year-old in Kerala, who had tested positive for West Nile Virus (WNV), died in Kozhikode on Monday. It is first reported death in India due to the WNV. West Nile Virus is a disease which spreads from birds to humans with the bite of an infected Culex mosquito. The symptoms include cold, fever, bodyache, fatigue and nausea, with complications leading to meningitis and death. Birds are natural hosts of the virus.
West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness. You can reduce your risk of WNV by using insect repellent and wearing long-sleeved shirts and long pants to prevent mosquito bites.
The WNV can cause neurological disease and death in people and is common in Africa, Europe, the Middle East, North America and West Asia.
Here is all about the virus:
What is West Nile virus? West Nile virus (WNV) is an infectious disease spread by infected mosquitoes. It spreads from birds to humans with the bite of an infected Culex mosquito.
What are the symptoms on WNV?
People who get WNV usually have no symptoms or mild symptoms. The symptoms include a fever, headache, body aches, skin rash, and swollen lymph glands. They can last a few days to several weeks, and usually go away on their own.
When is it dangerous?
If West Nile virus enters the brain, it can be life-threatening. It may cause inflammation of the brain, called encephalitis, or inflammation of the tissue that surrounds the brain and spinal cord, called meningitis.
How is WNV diagnosed
A physical exam, medical history, and laboratory tests can diagnose it.
Who are at risk?
Older people, children and those with weakened immune systems are most at risk.
What is the cure?
There are no specific vaccines or treatments for human WNV disease. The best way to avoid WNV is to prevent mosquito bites. Treatment is supportive for patients with neuro-invasive West Nile virus, often involving hospitalization, intravenous fluids, respiratory support, and prevention of secondary infections.
Have there been any outbreaks?
The largest outbreaks occurred in Greece, Israel, Romania, Russia and USA. Outbreak sites are on major birds migratory routes. In its original range, WNV was prevalent throughout Africa, parts of Europe,
Middle East, West Asia, and Australia. Since its introduction in 1999 into USA, the virus has spread and is now widely established from Canada to Venezuela.
In India : Since 2016, 124 cases of the disease have been reported from across the country, but no deaths.
Experts in virology say there is usually no single reason that leads to death in cases of WNV disease.
According to previous research, WNV is not a new disease to India.
In India, the existence of antibodies (protein produced by the human body to fight bacteria and viruses) against WNV in humans was recorded for the first time in 1952, according to a 2006 research paper titled “West Nile Virus isolates from India: evidence for a distinct genetic lineage”.
The research was conducted by experts at the National Institute of Virology in Pune, and published in the Journal of General Virology.
Since WNV is a vector-borne disease, the health ministry has been monitoring the situation closely. A team of experts from health ministry’s National Centre for Disease Control has been assisting state authorities
The most effective way to prevent infection from West Nile virus is to prevent mosquito bites. Mosquitoes bite during the day and night. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and take steps to control mosquitoes indoors and outdoors.
Take steps to control mosquitoes indoors and outdoors
- Use screens on windows and doors. Repair holes in screens to keep mosquitoes outdoors.
- Use air conditioning, if available.
- Stop mosquitoes from laying eggs in or near water.
- Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.
- Check indoors and outdoors.
There is no specific treatment for WNV disease; clinical management is supportive. Patients with severe meningeal symptoms often require pain control for headaches and antiemetic therapy and rehydration for associated nausea and vomiting. Patients with encephalitis require close monitoring for the development of elevated intracranial pressure and seizures. Patients with encephalitis or poliomyelitis should be monitored for inability to protect their airway. Acute neuromuscular respiratory failure may develop rapidly and prolonged ventilatory support may be required.
WNV Antibody Testing
Laboratory diagnosis is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect WNV-specific IgM antibodies. Immunoassays for WNV-specific IgM are available commercially and through state public health laboratories.
WNV-specific IgM antibodies are usually detectable 3 to 8 days after onset of illness and persist for 30 to 90 days, but longer persistence has been documented. Therefore, positive IgM antibodies occasionally may reflect a past infection. If serum is collected within 8 days of illness onset, the absence of detectable virus-specific IgM does not rule out the diagnosis of WNV infection, and the test may need to be repeated on a later sample.
The presence of WNV-specific IgM in blood or CSF provides good evidence of recent infection but may also result from cross-reactive antibodies after infection with other flaviviruses or from non-specific reactivity. According to product inserts for commercially available WNV IgM assays, all positive results obtained with these assays should be confirmed by neutralizing antibody testing of acute- and convalescent-phase serum specimens at a state public health laboratory or CDC.
WNV IgG antibodies generally are detected shortly after IgM antibodies and persist for many years following a symptomatic or asymptomatic infection. Therefore, the presence of IgG antibodies alone is only evidence of previous infection and clinically compatible cases with the presence of IgG, but not IgM, should be evaluated for other etiologic agents.
Plaque-reduction neutralization tests (PRNTs) performed in reference laboratories, including some state public health laboratories and CDC, can help determine the specific infecting flavivirus. PRNTs can also confirm acute infection by demonstrating a fourfold or greater change in WNV-specific neutralizing antibody titer between acute- and convalescent-phase serum samples collected 2 to 3 weeks apart.
Other testing for WNV disease
Viral cultures and tests to detect viral RNA (e.g., reverse transcriptase-polymerase chain reaction [RT-PCR]) can be performed on serum, CSF, and tissue specimens that are collected early in the course of illness and, if results are positive, can confirm an infection. Immunohistochemistry (IHC) can detect WNV antigen in formalin-fixed tissue. Negative results of these tests do not rule out WNV infection. Viral culture, RT-PCR, and IHC can be requested through state public health laboratories or CDC.
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