Russia warns of increase in West Nile Virus cases: What is it? What are its symptoms?

On Monday, Russia issued a warning about the possibility of a rise in West Nile Virus (WNV) infections this autumn citing mild temperatures and heavy precipitation as favourable circumstances for mosquitos that carry the virus.

“In light of favourable climatic conditions this year - an abundance of precipitation… a warm and long autumn, a high number of (virus) carriers could be observed in the autumn," Rospotrebnadzor, Russia’s consumer health watchdog, said.

Over 80 percent of West Nile fever cases in Russia are registered in the country’s southwest.

So what is the West Nile Virus (WNV)?

As per the World Health Organisation, the West Nile Virus (WNV) is a member of the flavivirus genus and belongs to the Japanese encephalitis antigenic complex of the family Flaviviridae.

It is an infectious disease spread by infected mosquitoes. According to the Centers for Disease Control and Prevention (CDC), it 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.

About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness due to the West Nile virus recover completely, but fatigue and weakness can last for weeks or months.

What are its symptoms?

Infection with WNV is either asymptomatic (no symptoms) in around 80 percent of infected people, or can lead to West Nile fever or severe West Nile disease.

About 20 percent of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, nausea, vomiting, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands.

About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

• Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.
• Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk for severe illness if they are infected (1 in 50 people). People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
• Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.
• About 1 out of 10 people who develop severe illness affecting the central nervous system die.

How to diagnose WNV?

West Nile virus can be diagnosed by a number of different tests:

• IgG antibody sero-conversion (or significant increase in antibody titers) in two serial specimens collected at a one-week interval by enzyme-linked immunosorbent assay (ELISA)
• IgM antibody capture enzyme-linked immunosorbent assay (ELISA)
• neutralisation assays
• viral detection by reverse transcription-polymerase chain reaction (RT-PCR) assay
• virus isolation by cell culture.

IgM can be detected in nearly all cerebrospinal fluid (CSF) and serum specimens received from WNV infected patients at the time of their clinical presentation. Serum IgM antibodies may persist for more than a year.

How to treat WNV?

No vaccine for humans is currently available.

Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms

However, treatment for patients with neuro-invasive West Nile virus often involves hospitalisation, intravenous fluids, respiratory support, and prevention of secondary infections.