West Nile Virus Terms
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A Glossary of West Nile Virus Terms and Definitions – An Emerging Disease that we don’t want to emerge at all

West Nile virus has been in the news a lot recently, it is one of those 'emerging diseases' that just seem to spring up out of nowhere, and cause a lot of public consternation.

And it’s certainly wise to be concerned about such matters, though there is no need for panic as by far the majority of cases develop no symptoms at all. But of course not all are so lucky, and around 20% will suffer from the short term effects of West Nile Fever (WNF) and unfortunately 1% of those people that become infected will probably become seriously ill with unpleasant diseases such as West Nile encephalitis or meningitis.

So, let’s now have a look through a selection of terms and definitions about the West Nile Virus:

  • Active Ingredients
    Those ingredients of chemical sprays that are directly responsible for the task in hand, rather than for aiding with formulation, or present for other reasons. (See also Inert Ingredients).

  • Adulticides
    These are insecticides designed to kill adult mosquitoes (amongst others) which carry and transfer diseases. (See Insecticides and Pesticides).

  • Antibodies
    Substances formed in the blood as a counteractive to infectious agents called antigens. (See Seroprevalence Surveys).

  • Antigen
    A toxic substance in the blood which the body reacts to by forming antibodies.

  • Arbovirus
    This is a abbreviation of 'arthropod borne virus' and includes around 300 different viruses as well as West Nile virus, that are carried and spread by arthropods (particularly though not exclusively mosquitoes).

  • Arthropods
    Invertebrate (without backbone) animals with jointed limbs and segmented bodies like all insects, spiders and crustaceans. The word comes from the Greek for joint, 'arthron' and foot, 'podos.'

  • Avian Surveillance
    The regular monitoring of local bird populations for signs of West Nile virus or other diseases.

  • Bridge Vector
    See Vector.

  • BTi (Bacillus Thuringiensis israelensis)
    Bacteria that are utilized as a biological pesticide for the killing of mosquito larvae underwater.

  • Carrier
    Anything that carries and transmits disease whilst not itself being affected by that disease.

  • Case Fatality Rate (CFR)
    This is the percentage number of those people who are diagnosed as infected with a particular disease, and subsequently die because of it.

  • CDC
    Centers for Disease Control and Prevention. Visit this United States governmental organization’s website at www.cdc.gov.

  • Chemical Specific
    A fact that is used to reinforce the fact that each individual chemical in this field has unique RfCs and RfDs. (See RfC and RfD).

  • Communicable Diseases
    Diseases that are spread through infectious agents which can be transmitted directly or indirectly from person to person, animal to person etc.

  • Culex Pipiens
    A very common species of mosquito that is the main vector for West Nile Virus in the United States. (See Vector).

  • DEET
    This is the active ingredient in a lot of insect repellents. Its chemical name is N,N-diethyl-meta-toluamide. (See Active Ingredients).

  • Degrade
    This is where a complex chemical (sprays for example) breaks down into simpler compounds to have a lesser effect on the environment over the long term.

  • Deposition Levels
    These are scientific estimates of the amount of adulticide that would settle on people, soil, food, water, buildings etc. after spraying, and what level of concentration the ingredients of the spray would be found in. (See Adulticide and Exposure Pathways).

  • Drift
    The varying amounts of adulticide spray which is lost to the targeted area because of the effects of wind. (See Adulticide).

  • Effective Concentration
    This is an estimate of how much of the active ingredients in an adulticide will be breathed in daily by people within the given area due to be sprayed. (See also Active Ingredients).

  • EIS (Environmental Impact Statement)
    An important document that is used to state what impact (in the case of West Nile Virus - adulticide spraying) will have on the overall environment.

  • Encephalitis
    A serious condition involving the inflammation of the brain which can be caused by bacterial infection, or numerous viruses, one of which is the West Nile Virus.

  • Endemic
    An endemic disease is one that is always present in the population of a given area, and so can be expected to occur with predictable regularity within that specific region. (See also Epidemic and Pandemic).

  • Enzootic
    These are diseases of animals which occur regularly, and are always present in a given region.

  • Epicenter (of viruses)
    This is the geographical location where an outbreak of a virus first occurs in humans.

  • Epidemic
    The outbreak and occurrence of a disease that afflicts a large number of people at once in a given area. The disease may either be carried in from somewhere else, or be a sudden though short term increase of an endemic disease. (See also Endemic and Pandemic).

  • Epidemiological Studies
    Studies which seek to find out why (or why not) a disease or disease causing agent is present.

  • Epidemiology
    The specific branch of medicine that concerns itself with occurrences and spread of disease in a population, and its eventual (hopefully) control.

  • Epizootic
    A disease outbreak which affects many animals simultaneously.

  • Exposure Pathways
    These are the various ways and means that people and animals can come into contact with an adulticide after it has been sprayed onto any area. The spray being breathed in, or contaminating food crops are just two examples of the possibilities in which people interact with a change in their environment. (See also Deposition Levels).

  • Febrile
    Pertaining to fever or a state of feverishness.

  • Febrile Illness
    An ailment where a fever is present.

  • Flavivirus
    This is the family of viruses to which the West Nile Virus belongs. It also contains others such as St. Louis Encephalitis; which was initially thought to be the culprit for the first outbreaks of WNV in the United States.

  • Gravid Traps
    These are types of mosquito traps specifically intended for female mosquitoes that are 'pregnant' (filled with eggs).

  • HI (Hazard Index)
    This is the total of all the differing Hazard Quotients for each active ingredient in the adulticide across all the exposure pathways for each sector of the population. It is the entirety of exposures for each active ingredient expressed numerically.

    If less than 1.0 then no ill health results are expected (not including cancers), but if the hazard index stands greater than 1.0 after the equations have been worked out, then more checks will be needed. (See also Active Ingredients, Adulticide, Exposure Pathways, and HQ).

  • Host
    A human or animal that has a parasite (in this case the West Nile Virus) present within their bodies. Viruses are parasites because they are organisms which need a living host in which to reproduce themselves.

  • HQ (Hazard Quotient)
    This is a ratio that compares the average daily dose of a specific exposure pathway with the acceptable daily dose of the same. It is a way of keeping watch that any ill health risks are kept to a bare minimum. (See also Exposure Pathways and HI).

  • Inert Ingredient
    In chemical products; these are the parts of the chemical make-up of the substance (often solvents) which do not, say in the case of insecticides or insect repellants, kill or repel the insects, but instead aid with the dispersal or formulation of the active ingredients which do the work. (See also Active Ingredients).

  • Insecticides
    A particular category of pesticides which are used to kill insect pests.

  • Larvae
    The immature stage of mosquitoes which they develop into underwater after emerging from their eggs. Any standing water will suffice, and they can often be seen near the surface using breathing tubes. (See below and Oils).

  • Larviciding
    This is the use of pesticides for killing undeveloped mosquitoes while they are still in their aquatic larval stage. Mosquitoes do not bite or transmit disease while still immature. (See Bti and Mosquitoes).

  • Meningitis
    An inflammation of the membranes that line the brain and the spinal cord.

  • Meningoencephalitis
    This is where both the brain itself, as well as the lining of the brain and the spinal cord is inflamed.

  • MOE (Margin Of Exposure)
    This analysis method is one recommended by the USEPA (United States Environmental Protection Agency) for considering cancer risks.

  • MSDS (Material Safety Data Sheet)
    This is a list of the ingredients in a pesticide, and advice concerning their correct use and the associated health risks provided by the manufacturer.

  • Multivoltine
    In this case, mosquitoes which are capable of breeding more than once within a normal breeding season.

  • Non Target Biota
    The plants and animals in a sprayed area that are not the intentional targets of the pesticide.

  • Oils
    Spreading certain oils over the surfaces of standing water can be effective at killing mosquito larvae because it prevents them from breathing air via their 'snorkels.' (See Larvae).

  • Organophosphates
    These are a type of adulticides that kill insects by shutting down their central nervous system. Organophosphates are divided into groups, and there is some debate as to which are less toxic to humans and the environment in general, but the widespread use of any is often controversial. (See Adulticide).

  • Outbreak
    A sudden increase in either (or both) the number of occurrences and distribution of any disease.

  • Pandemic
    A disease that is prevalent across the whole population and cannot be restricted to any region. (See also Endemic and Epidemic).

  • Partitioning
    This is where a part of an active ingredient leaves the air or water say, where it was applied and enters the soil, whilst the rest remains. (See Active Ingredients).

  • Pathogen
    Any organism (in this case a virus) that is the cause of disease.

  • Pathways
    See Exposure Pathways.

  • Pesticides
    Chemicals designed to kill various pests which are sub-divided into categories. Use of pesticides can sometimes be highly controversial, and some people are convinced that in many cases they do more harm than good to the environment.

  • Phased Approach
    This is a way of vector surveillance and control which takes many factors into account; some of which is; the time of the year; current and prevailing weather; the level of virus presence in both vectors and humans, and the population density of vectors and nearby humans. (See also Vector, Vector Control and Vector Surveillance).

  • Proboscis
    The name of the long mouthparts which mosquitoes use to pierce through animal and human skin, and suck up blood with; sometimes thereby being the cause of unintentionally transmitted disease like West Nile Virus and many others.

  • Pupa
    The stage of a mosquito’s life cycle between that of the larval and the flying, biting adult. (See Larvae).

  • Pyrethrin
    A natural insecticide that is derived from plants.

  • Reservoir
    An animal (but sometimes human) population where a disease is widespread and hosted before being transmitted to other animals or humans. In the case of West Nile Virus, the reservoir is wild birds which are bitten by mosquitoes. These infected mosquitoe bites pass the disease along from one species to another.

  • RfC (Reference Concentration)
    This is a measure of the amount of a specific chemical that people can be exposed to daily, without any directly resulting ill health by breathing it in. (See below and also Chemical Specific).

  • RfD (Reference Dose)
    This is a measure that differs from the Rfc as it is a chemical specific dose that people can be exposed to daily, by either ingestion or skin contact, without any directly attributable ill health concerns. The word 'chronic' can be used ahead of this to mean; in the long term. (See above and Chemical Specific).

  • Sentinel Chickens
    These are used as an early warning for virus outbreaks.

  • Seroprevalence Surveys
    These are surveys carried out on blood samples by public health authorities. They check the blood serum for the presence of antibodies to particular infections, which then give pointers as to what percentage of a local population have come into contact with (in this case) West Nile Virus within a close timeframe. (See also Antibodies).

  • Serosurveys
    See above.

  • Source Reduction
    This is the vital task of reducing areas where mosquito larvae can thrive in any given locality. Individual citizens can help in this task by clearing out any brackish water on their properties or in their neighborhoods.

  • Surveillance
    The monitoring of animal populations to check for the presence of the virus.

  • Toxicity Analysis
    Part of an overall risk assessment, this is an important stage in deciding whether to spray insecticides. The analysis must gauge what quantities of the chosen adulticide must be used in order to be effective without adversely risking the public. Because some amount of exposure is inevitable, just how much can be allowed for, at levels where the risk is negligible, must be quantified.

  • USEPA Toxicity Classes
    The USEPA (United States Environmental Protection Agency) divides adulticide into four classes relative to their toxicity towards humans and other mammals, fish, and birds. This takes into account possible ingestion of the toxins (poisons) as well as the risk of breathing them in and of course, skin contact. (See Adulticide).

  • Vector
    A transmitter and carrier of disease pathogens, in this case - the mosquito. (See Pathogen).

  • Vector Control
    Measures taken to control the vector numbers (spraying adulticide is one obvious example of this).

  • Vector Surveillance
    This is the monitoring of vectors (in the case of West Nile Virus in North America - the mosquito) to see how prevalent the disease is amongst them.

  • Vertical Transmission
    This is where an infected female mosquito will pass the virus on to her eggs.

  • Viral
    Pertaining to a virus.

  • Viremic
    This word means that a host has a virus present in their blood.

  • Viruses
    Living microscopic organisms that need living hosts to reproduce in. Their presence can cause infectious diseases which are sometimes mild, and sometimes severe.

  • Weight Of Evidence Approach
    This is where information and studies from various sources, and regarding various aspects of environmental and public concerns are combined when 'weighing up' the decision of if, where and when to spray adulticide. (See Adulticide).

  • West Nile Virus Encephalitis
    Inflammation of the brain as caused by WNV.

  • WNF
    An abbreviation for West Nile Fever.

  • WNV
    An abbreviation often used for West Nile Virus.

  • Zoonotic
    These are diseases, of which West Nile Virus is one, where the pathogens are not only hosted by humans, but other animals as well, and that the disease is communicable from these animals to the human population. (See also Host and Pathogen).

There’s some info then, about the subject of the West Nile virus. First recognized in the West Nile province of the African country of Uganda in the thirties (hence its name), it spread through Africa, Asia and parts of southern Europe before arriving five years ago in North America with all that sudden publicity of the 1999 New York outbreak.

Although it is relatively unlikely (statistically speaking) for an individual to get infected, and even less likely to develop serious disease because of it, it is still better to take no chances with any high fever combined with very bad headaches - if you or a loved one have these, then always seek medical attention immediately.

About The Author

Matt Jacks is a successful article writer for hire providing tips and advice for consumers about mosquito control, West Nile Virus and how to use mosquito repellant safely. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.

This "Glossary of West Nile Virus Terms and Definitions" reprinted with permission.

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