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
Prevention
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.
Treatment
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.