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West Nile Virus

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Contingency plan and downloadable product information sheets


HSE has contributed to a contingency plan developed by the Department of Health (DH) to set out procedures to be followed in the event of an outbreak of West Nile virus (WNV) in the UK. The contingency plan was issued in May 2004.


WNV may be transmitted from certain species of animal to humans by mosquitoes and part of the contingency plan involves the control of mosquitoes using products regulated by HSE. Ministers have agreed extensions to the use areas of certain insecticide products as part of a WNV control plan, subject to particular conditions of use.

Product extensions (additional use areas)

Certain products containing Bacillus thuringiensis var israelensis (Bti) may now be used on permanent waters to control mosquito larvae in the event of a WNV outbreak. Such products are known as 'larvicides'.

Particular products containing certain pyrethroid active ingredients may now be used outdoors to control adult mosquitoes in the event of a WNV outbreak. Such products are known as 'adulticides'.

These extensions are specific to mosquito control in the event of an outbreak of WNV. Mosquito control in such areas in the absence of a WNV outbreak is not permitted. Before treatment of mosquitoes associated with an outbreak of WNV may take place, the procedures specified in the DH contingency plan must be followed.

Products to be used during an outbreak of WNV

The following products with downloadable information sheet may be used to control mosquitoes during an outbreak of WNV:

Preferred product

Other products

The preferred products for adult mosquito control result from Ministers agreeing that these contain active substances that pose the least risk to the environment under the conditions set in place for WNV control. In the event of a serious outbreak of WNV in the UK (as specified in the DH's contingency plan), coupled with supply shortages of preferred products, the other products that are available for adult mosquito control during such an outbreak should be considered. Products that do not have a downloadable information sheet and that have not been considered for use against mosquitoes during an outbreak of WNV should not be used.

The downloadable information sheet

The above downloadable information sheet are available for pest control operators to use when necessary during an outbreak of WNV. Users should download the labels as required, print them off, familiarise themselves with them (paying particular attention to the conditions of use) and have them to hand during treatment of mosquitoes as part of any WNV control programme.

Pest control operators are reminded of the requirement to undertake a COSHH assessment prior to going ahead with any treatment.

Updated 2020-11-23