Louisiana Officials Report West Nile Virus in Decline

Despite one reported death from West Nile virus in November 2015, Louisiana health officials report a decline in the occurrence of the mosquito-borne illness.

Louisiana State Health Department showed 65 cases in 2015 as compared to 135 in 2014. The outbreak in 2012 involved 360 cases resulting in 15 deaths.

West Nile virus is transmitted by mosquitos. It cannot be transmitted person to person or animal to person.

Louisiana has taken steps to control the major carrier, the common Southern house mosquito, with aerial spraying. The US Environmental Protection Agency allows spraying only in wind conditions below 10 mph. A scheduled spraying last fall had to be cancelled due to high winds. The public is encouraged to monitor property for standing water such as wading pools.

Individuals can reduce their risk by using mosquito repellents, wearing long-sleeved clothing and long pants, and limiting outdoor exposure, especially from dusk to dawn. The use of air-conditioning and window/door screens can further reduce West Nile Virus exposure.

Symptoms of West Nile virus

The Centers for Disease Control and Prevention report that 70-80% of people infected with West Nile Virus do not develop symptoms. The most common symptoms include headache, body ache, joint pains, vomiting, diarrhea, or rash. Full recovery can be expected within two weeks with fatigue and weakness lingering for a few weeks or months. Less than one percent of infected individuals develop more severe neurologic symptoms such as headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.

Individuals over 60 years of age are at greatest risk for more severe symptoms. Others at risk include patients with existing medical conditions such as cancer, diabetes, hypertension, kidney disease, and people who have received transplanted organs. Recovery in severe cases may take weeks or months. Some neurologic effects may be permanent.

Ten percent of those who develop neurologic infection from West Nile virus will die from the virus, according to the CDC.

Diagnosis of West Nile virus

A laboratory diagnosis is determined by anti-body testing of serum or cerebrospinal fluid to detect for West Nile viral-specific IgM antibodies. These are usually detectable three to eight days after the onset of illness and persist for 30 to 90 days.

Viral cultures and tests to detect viral RNA can be performed on serum, CSF, and tissue specimens that are collected early in the course of the illness. Immunohistochemistry (IHC) can detect West Nile Virus antigen in formalin-fixed tissue. Contact state public health laboratories or the CDC for more information.

Treatment of West Nile virus

There is no vaccine or specific antiviral treatment for West Nile virus. Treatments include over the counter pain and fever reducers and rehydration treatments associated with the symptoms of vomiting and diarrhea. Patients with more severe symptoms can receive supportive treatment in a hospital setting.

Some drugs and treatments are being studied as described in this review of the literature for health care providers.