Human West Nile Virus Infections In Colorado, Texas And Mississippi

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Public Health
Article Date: 01 Jul 2006 - 7:00 PDT


The CDC has received reports of human West Nile Virus (WNV) infection in the states of Texas, Colorado and Mississippi. Experts are expecting this to be a bumper year for infections and ask everyone to take special precaustions.

Bird, animal or mosquito infections have been reported in several states:

-- Arkansas
-- California
-- Florida
-- Idaho
-- Illinois
-- Indiana
-- Iowa
-- Michigan
-- Minnesota
-- Missouri
-- Nebraska
-- New York
-- North Dakota
-- Ohio
-- Oklahoma
-- South Dakota
-- Tennessee
-- Texas
-- Utah
-- West Virginia
-- Wisconsin
-- Wyoming

Human West Nile Infection - What Happens?

80% of people who become infected with WNV show no symptoms and do not become ill. The other 20% develop what is known as West Nile Fever. WMV infection has an incubation period of 2-14 days - some immunosuppressed people have had longer incubation periods.

What are the Clinical Features of West Nile Fever?

-- Eye pain (on occasions)
-- Fatigue
-- Fever
-- Headache
-- Skin rash on the trunk of the body (on occasions)
-- Swollen lymph glands (on occasions)

Severe Complications

-- West Nile Meningitis
-- West Nile Encephalitis
-- West Nile Poliomyelitis

If the central nervous system is infected the patient may have clinical syndromes, such as febrile headache, aseptic meningitis or encephalitis. These syndromes are indistinguishable from those caused by other viruses.

60% to 70% of patients with neuroinvasive WNV infection have encephalitis or meningoencephalitis. 25% to 35% have meningitis without encephalitis.

West Nile Meningitis symptoms include fever, stiff neck and headache. Changes in consciousness are rare, and if present are very mild.

Headache is not a useful indicator for complications as it is common in WNV fever, meningitis and/or encephalitis.

West Nile Encephalitis has, apart from the symptoms of fever and headache, also: alteration of consciousness which may be mild and can develop into confusion or coma, tremors and movement disorders - it is not uncommon to observe localised neurologic deficits such as limb paralysis and cranial nerve palsies.

West Nile Poiomyelitis is a flaccid paralysis syndrome linked to WNV infection. It is much less common than meningitis or encephalitis. There is no sensory loss, but limbs are weak and/or paralysed. It is not uncommon for the patient to feel pain before the paralysis. There is not always fever present for paralysis to occur. Respiratory failure is possible as well.

Severe Disease Clinical Features

-- Fever
-- Gastrointestinal symptoms
-- Ataxia and extrapyramidal signs
-- Optic neuritis
-- Seizures
-- Weakness
-- Change in mental status
-- Myelitis
-- Polyradiculitis
-- A small percentage of patients with severe disease develop a rash on the neck, trunk, arms or legs.

-- Avoiding Mosquito Bites (CDC)

-- West Nile Virus Fact Sheet (CDC)

-- West Nile Virus Q & A (CDC)

-- Maps with county-level human, mosquito, veterinary, avian and sentinel data

Written by: Christian Nordqvist
Editor: Medical News Today
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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