WEST NILE VIRUS
A HEALTH UNDERWRITING PERSPECTIVE

Hank George, FALU, CLU, FLMI
Risk Concepts

A question was raised by a member of the Health Underwriting Study Group (HUSG) regarding the morbidity issues associated with WEST NILE VIRUS and its medical consequence known as WEST NILE ENCEPHALITIS. This overview may be of value to our website visitors who must confront this new and challenging issue in insurability.

WHAT IS THIS ENTITY WE CALL “WEST NILE VIRUS?”

Back in 1999, in NY City, a mysterious condition – provoked by sick birds – caused an outbreak of a cluster of cases of human encephalitis (brain inflammation). Since that time, this condition has spread across North America, causing thousands of cases and a few hundred deaths. It is also present in Europe, Africa and parts of Asia.

At last count, WEST NILE VIRUS was present in all but six US states…a few between Colorado and California being spared at this writing.

In Canada, a map in one of the articles show the virus present from New Brunswick to Southern Saskatchewan and a bit of Alberta. The only virus-free areas as of last year in The Great White North were British Columbia, probably Edmonton and possibly Calgary, the sparsely populated regions of the Yukon and Northwest Territories, Nova Scotia and Newfoundland (and there is the matter of whether some behavioral and mental status symptoms would be recognized as genuinely abnormal in Newfies anyway!)

This virus was first identified in 1937 in England. It is a blood-borne virus, transmitted by mosquitoes, most notably to birds. Jays and crows seem most at risk for the virus. The virus is a distant cousin of another flavivirus, the St. Louis encephalitis virus, which reeked havoc here decades ago.

The finding of clusters of dead birds raises the question of an outbreak.

WHAT ARE THE RISK FACTORS FOR ACQUIRING WEST NILE VIRUS INFECTION?

Being outdoors extensively, sans mosquito repellent, during mosquito “season,” is the #1 risk factor. Mosquitoes, not birds, spread the virus to humans.

Some people with very damp or flooded basements will have mosquito infestations. Not a good thing to have whenever there is evidence of the virus – again, via the discovery of dead birds in unusual numbers – in the vicinity.

Will eating dead birds cause infection?

I, for one, do not intend to find out!

HOW IS THE DIAGNOSIS MADE?

There are ELISA and PCR (polymerase chain reaction – very expensive) tests for WEST NILE VIRUS itself. However, the virus is not in the body very long and testing needs to be done as soon as the symptoms appear. For this reason, only about half of patients have a definite diagnosis made based on testing for the actual virus.

Testing for specific antibodies can apparently be done at any time – or at least for an extended period after recovery - once the infection has taken hold and provoked a host response. Those who lack antibodies are at very high risk for a fatal outcome because of impaired immunity.

WHAT ARE THE MEDICAL IMPLICATIONS OF INFECTION?

It is important to note that > 80% of infected persons are completely asymptomatic, don’t even know they have it and “recover” fully.

Only 1 in 5 gets a flu-like febrile illness, which may well be mild.

The incubation period is short; from 2 to 14 days depending on host resistance. The flu-like illness has the usual features: chills, tiredness, head and back pains, joint and muscle pains, and pain behind the eyeballs (retro-orbital pain).

Some patients develop generalized lymph node enlargements. A distinctive rash occurs in about 50%, especially children. Liver (20%) and spleen (10%) enlargements are uncommon. Because of the acute presentation in symptomatic persons, the hepatomegaly, splenomegaly and lymphadenopathy should not raise serious concerns for more insidious pathologies such as lymphoma or metastatic cancer.

Neurologic symptoms may arise, including impairment of limb function and even respiratory muscle function (thus requiring mechanical ventilation until the problem resolves or…).

Other neurologic symptoms include paralysis, cranial nerve dysfunction, optic neuritis (which would otherwise be mistaken for MS), tremors, ataxia (staggering gait, mistaken sometimes for being “in the bag” or “loaded” if you get my meaning!), and so on. But only about 1 in 150 patients have these problems.

Older people and persons with any immunological deficiencies are at highest risk for a fatal outcome. Most but not all healthy people recover. Nevertheless, the majority who go through the full-blown illness will some residual effects. It is said that only about 1 in 3 actually are 100% free of sequelae and recover completely in the fullest sense (being back to normal as they perceive it, as they were prior to being infected).

The risk factors for a fatal outcome are going into a deep coma at any time, failure to have a sustained IgM (immunoglobulin M) response to the infection and being afflicted with comorbidities - such as heart disease, lung disease or diabetes - that complicate the viral impact.

HOW IS WEST NILE VIRUS TREATED?

There are no specific treatments. There has been some success with interferon alpha and with ribavirin, drugs also used for chronic hepatitis C.

Most current treatment is supportive, targeted at specific symptoms and complications.

WHAT ARE THE OUTCOMES OF SIGNIFICANCE TO INSURABILITY?

Mortality is around 1 in 10 who get the full-blown syndrome. But this is higher at older ages and in diabetics.

Morbidity, alas, is more substantial at all ages.

At least half of “recovered” patients have significant difficulties after discharge from the hospital and cannot return to work. The major lingering problems are related to impaired memory, persistent fatigue and malaise, and neurologic residuals such as gait disturbances.

From a health underwriting point of view, anyone who has been identified as infected but has not developed more than the transient signs and symptoms – without complications – should be insurable with a brief waiting period after ostensible recovery.

Recovery, in the sense of disappearance of all acute symptoms and manifestations, usually takes places between 30 and 45 days. Some residual lymphadenopathy may occur, of course…but this happens in many infectious diseases that evoke an immune response and should not be an issue for insurance.

In cases where there are residuals, the issue of health insurability depends on their extent and thus the degree of intervention that may be needed.

Mild residuals would not pose a problem.

Those that require physical therapy and/or any other form of treatment could be problems.

The bottom line is that each case needs to be assessed individually and it is really impossible to come up with a unitary practice for those who recover with significant impairing sequelae.

WHAT DOES THE FUTURE PORTEND?

Bad news: WEST NILE VIRUS is apt to be around for a long time.

Good news: a vaccine should be available in the not-to-distant future.

Final statement: As I said in JOURNALSCAN [8,1(January, 2004):8], the bigger and more ominous issue for insurers is the appearance of a number of challenging viruses that have impacted large numbers of people: HIV, then WEST NILE, then SARS.

The question is: what’s next?

REFERENCES

Gelfand. POSTGRADUATE MEDICINE. 114,1(2003):31
George. Hank’s JOURNALSCAN. 8,1(January, 2004):8
Huhn. AMERICAN FAMILY PHYSICIAN. 68,4(2003):653
Petersen. JOURNAL OF THE AMA. 290,4(2003):524
Sampathkumar. MAYO CLINIC PROCEEDINGS. 78(2003):1137
Solomon. BRITISH MEDICAL JOURNAL. 326(April 19, 2003):865
Wagner. CLINICAL CHEMISTRY NEWS. September, 2003:12