CDC: ” We are in the midst of one of the worst outbreaks of West Nile Virus the USA has ever seen”

Figures released by the CDC on August 22 reveal that there have been 1118 reported cases of West Nile Virus, a three fold increase over the normal levels for this time of year. Of those cases reported, half have been inTexas where 21 of the 41 recorded deaths have also taken place. The rest of the cases are split between, South Dakota, Mississippi, Oklahoma and Louisiana. Of these 1118 case 629 have been serious cases that have progressed, becoming neuro-invasive. Lyle R Petersen  the Director of the Division of Vector-Borne Diseases at the CDC gave a briefing during which he said:

” We are in the midst of one of the worst outbreaks of West Nile Virus the USA has ever seen” Petersen, who contracted the disease himself in 2003 went on to say that anyone who survives the condition has life-long immunity from the disease.

WHAT IS IT?

Officially is is one of the Japanese encephalitis antigenic complex viruses of the family Flaviviridae. As stated it is a virus and it is spread by mosquitoes of the genus culex, particularly culex Pipiens and it is maintained by vertical transmission (adult to egg). This is not the genus of mosquito that spread malaria. Birds are the natural reservoir of the disease and mosquitoes pick it up by feeding on infected birds. They then pass it through their bite to other animals and humans.

The United States is so far unique in that the virus is highly pathogenic to its birds with the crow family being particularly susceptible although it has been found in 250 species of birds, all who were dead or dying.

In Europe, Asia, the Middle East and Africa morbidity and mortality in the birds is rarely found, they appear healthy.

It can also be spread by contact with infected blood from other animals, and rarely through blood transfusion, organ transplantation and pregnancy.

SYMPTOMS
* high temperature 101.4*F (38*C)
* headache
* backache
* muscle aches
* sore throat<
* nausea
* vomiting
* diarrhoea
* swollen lymph glands in the neck
* rash on stomach back and chest

These symptoms usually appear 3-15 days after infection occurs. The more serious, neuro-invasive cases show the above symptoms and in addition may present with:
* sore eyes
* disorientation
* shaking
* seizures/fits/convulsions
* stupor/coma
* muscle weakness

These symptoms usually precede encephalitis, meningitis or paralysis. People over the age of 50 are more likely to develop the serious form of the disease than are younger people.

TREATMENT

There is no specific treatment for West Nile Virus. As a virus antibiotics have no effect. The milder form usually clears of its own accord within a few days to a few weeks and there are rarely any lasting effects after recovery. The more serious cases do not have such a good prognosis and although people do recover it is possible they may be left with brain damage from encephalitis and meningitis can lead to meningococcal septicaemia with the resultant loss of one or more limbs. Very severe cases can lead to death through either of the above conditions. Medical care is IV infusions to maintain hydration, IV antibiotics if secondary infection is suspected and ventilatory support as required.

AVOIDANCE
* decent mosquito repellant containing DEET
* long sleeves and long trousers
* screens on windows and doors
* citronella or other bug repellant candles
* draining of stagnant water and un-used swimming pools
* community spraying to prevent mosquitoes breeding

The fact that only 1  in 150 people usually develop the severe form of the disease, but  in this outbreak more than half have developed it, is the reason the authorities are spraying with such vigour in an attempt to control the spread of the disease. One report, from the BBC suggests they are spraying a substance called DUET, based on extract of chrysanthemum which is not harmful to animals and humans but deadly to mosquitoes. I have found no other mention of DUET so I cannot verify that this is indeed the substance being sprayed.

Take care

Lizzie