Disease profiles
×
Disease events
From
To
Disease situation (Filter animal category)
From
To

Geographical distribution

Based on official disease reports to the WOAH

West Nile is a disease listed in the World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code. The map to the right displays occurrence reported to the WOAH-WAHIS system since 2005.

As described in the WOAH Terrestrial Animal Health Code, the WOAH early warning system includes immediate notifications and follow-up reports on:

  • First occurrences of a listed disease,
  • Recurrence of an eradicated listed disease,
  • First occurrences of new strain of a pathogenic agent of a listed disease,
  • Recurrence of an eradicated strain,
  • Sudden and unexpected changes in the distribution or increase in incidence or virulence of, or morbidity or mortality caused by the pathogenic agent of a listed disease
  • Occurrence of a listed disease in an unusual host species.

Countries are coloured according to the available information regarding their stable disease situation (disease situation legend). This information is provided by countries through the WOAH monitoring system, which is a different reporting channel.
The disease situations (country/region colours) are prioritized in the following order: Present, Suspected and Absent if more than one is present in a country during the filtered period.
Immediate notifications (points) and disease situation (country/region colours) are reported to the WOAH in different spatial and temporal scales, and therefore are displayed in the map as layers which can be filtered independently.

Last updated at: 2024-11-18

For more up to date reports, visit the original data source: WOAH-WAHIS.

Epi studies

Epidemiological studies investigating disease dynamics and measures of disease frequency

The panel to the right shows the distribution of epidemiological studies collected in the literature review. Click on the map to see more information about the studies. The following study context categories are considered:

  • Case reports
  • Passive surveillance (reports of specific surveillance activities following reported cases)
  • Evidence of disease freedom (investigations to confirm disease absence)
  • Observational study (case-control or cohort studies)
  • Active surveillance (active testing of animals and search for cases)
  • Survey (designed sampling and testing of animals)

It is important to note that studies targetting humans were NOT included in the systematic literature reviews.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Disease

Animal Health Impact

A summary of the disease in animal hosts is given in the WOAH Technical disease card.

The panel to the right summarizes evidence collected from published studies describing natural infections with this agent (as opposed to experimental infections, summarized in dedicated section).

It is important to note that studies targetting humans were NOT included in the systematic literature reviews.

Public Health

Human infections are mostly asymptomatic. However, in some cases, they can exhibit a mild form of the disease associated with fever, malaise, loss of appetite, nausea, vomiting, headache and myalgia. Severe cases (less than 1%) with signs of encephalitis, meningoencephalitis or meningitis can be observed among elderly or immunosupressed individuals (Go et al., 2014).

EFSA conducts regular systematic literature reviews covering studies investigating natural infections with this agent, and published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Experimental Inf.

The panel to the right summarizes all evidence collected by EFSA from published experimental infection studies describing the health effects of this pathogen in host animal species. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

  • Host species
  • Start of clinical signs (incubation period)
  • Duration of clinical signs
  • All diverse types of clinical signs reported in the different host species
  • Case fatality
  • Meta-analysis of the reported duration of observable clinical signs, accounting for censoring in the experimental infection study groups

EFSA conducts regular systematic literature reviews covering all experimental infections published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Agent

Virus taxonomy

Family: Flaviviridae

Genus: Flavivirus

Species: West Nile virus

Virus survival outside living hosts

The panel to the right summarizes all evidence collected by EFSA from published experiments on pathogen survival. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

  • Survival plots indicating the maximum number of days the virus was detected in different matrices under different conditions (temperature)
  • Half-life studies which documented virus viability decay over time under different temperatures
  • Meta-analysis of the reported virus survival period for matrices in which a sufficient number of studies were found

EFSA conducts regular systematic literature reviews covering pathogen survival experiments published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Transmission

The panel to the right summarizes all evidence collected by EFSA from published experimental infection studies describing host infectiousness. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

  • Evidence of Host-host transmission
  • Evidence of transplacentary transmission
  • Meta-analysis of the reported duration of the infectious period, accounting for censoring in the experimental infection study groups
  • Data for all animal matrices in which agent presence was demonstrated.

EFSA conducts regular systematic literature reviews covering all experimental infections published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Diagnosis

WOAH-prescribed tests for international trade include (WOAH, Terrestrial Manual):

  • For the detection of the agent (confirmation of clinical cases and individual animal freedom from infection prior to movement): nested RT-PCR, real time RT-PCR, immunohistochemistry and isolation in tissue culture.
  • For detection of immune response: CIgM capture ELISA, IgG indirect and competitive ELISAs, plaque reduction neutralisation and virus neutralisation.

EFSA conducts regular systematic literature reviews covering peer-reviewed literature in English since 1970, covering diagnostic tests approved for use in the European Union (EU).

Data were collected from all evaluations of performance of those tests which provided sensitivity or specificity (or enough data to estimate those needed to be provided). You can browse through the data collected scrolling the panel to the right.

We have chosen not to aggregate and summarize the results because the study conditions can vary greatly. Instead, we present the results for all the articles retrieved from the literature individually, grouped by type of test, diagnostic target and, when relevant, animal species.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Vectors

Know vectors
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Diptera
  • Family: Culicidae

Genera: Culex sp., Aedes sp., Coquillettidia sp

The map on the right shows the reported presence of mosquito species in primary sources.

Visit the VectorNet resources directly for further information on disease vectors, including expert opinion

*To consider an arthropod species as a vector for viruses, the following four criteria should be satisfied (World Health Organization, 1967): (1) the species should be repeatedly associated with the disease in the field (season and places); (2) the virus should be recovered from field-collected adult females that do not have a fresh blood meal in the abdomen; (3) the species should be able to become infected after oral infection; and (4) the species should be able to transmit the infection biologically. However, based on the literature finding, all these criteria could be satisfied for only very few arthropod species, which could then be called a vector in this strict sense. Furthermore, other vector species could be present which were never tested for this pathogen.

Vector control

The panel to the right summarizes all evidence collected by EFSA from published studies of the efficacy of various substances available for MOSQUITO control. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

  • The efficacy of various substances on vector mortality, when applied to animal hosts by different routes (modes of treatment)
  • The efficacy of various substances in experiments where vectors were directly exposed

Studies that presented substance effects through outcomes other than vector mortality (for instance infestation prevention)

EFSA conducts regular systematic literature reviews covering vector control studies (for selected vectors: midges, mosqtuitoes, sandflies and ticks) published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in January 2018. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Vaccination

EFSA conducts regular systematic literature reviews covering all vaccine efficacy studies published in peer-reviewed literature in English since 1970, when evaluating vaccines approved for use in the European Union.

The evidence collected from these references is summarized in the right panel.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in January 2018. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Treatments

The panel to the right summarizes all evidence collected by EFSA from published treatment efficacy studies. When available, evidence was collected from two main types of studies:

  • those in which the animals were subjected to a specific Pharmaceutical treatment, and the efficacy of the treatment in preventing infections in the treated group is reported in comparison to a control group;
  • and those in which a vector control substance (insecticide)t was used, and its effect in preventing infections in hosts is reported.

For both types of studies the panel to the right presents reported results regarding:

  • Efficacy: efficacy is measured as 1-(percentage infection in the treated group/percentage infection in the control group)
  • Titer of neutralizing antibodies
  • Percentage of positive animals (after exposire to the agent)
  • Mortality

EFSA conducts regular systematic literature reviews covering treatment efficacy studies published in peer-reviewed literature in English since 1970, when substances used for treatment are approved for use in the European Union.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in January 2018. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Legislation

In accordance with the Directive 2003/99/EC, Member States must collect, analyse and publish data on the occurrence of West Nile virus, in case the epidemiological situation so warrants. The monitoring data are reported to the European Food Safety Authority (EFSA) who validates and analyses them, and then publishes a situational (annual) summary for the EU as well as the data itself.

No specific measures are laid down in the EU legislation for WNV outbreak control. The EU does not apply any specific trade restrictions to prevent import of WNV.

EFSA Journal
Consult the available risk assessments in full through the links below:

Risk Assessments

EFSA regularly carries out risk assessments to support risk managers with their decision making on the prevention and control of diseases. Risk assessments of relevance for this disease are listed in the right panel.

Acknowledgments

Acknowledgments

The CoVetLab consortium has been responsible for the systematic literature reviews since 2015, and has delivered story maps to EFSA since 2021. Partners are: Swedish National Veterinary Institute (SVA, Sweden); Wageningen Bioveterinary Research (WBVR, The Netherlands); Animal and Plant Health Agency (APHA; UK) and the University of Surrey (UK).

Geographical distribution data has been kindly provided by the World Organisation of Animal Health (WOAH). WOAH-WAHIS (WOAH World Animal Health Information System) is the original source of these data.

References

The list of references displayed in this storymap is available on the right panel.

You can also download the complete list of references for each of the seven specific knowledge domains for which EFSA carries out systematic literature reviews regularly (living reviews):