|Scheduled airline traffic around the world, circa June 2009 – Credit Wikipedia|
Although infected travelers are the most likely way for Zika (or Dengue, CHKV, or malaria) to make it from endemic regions to North America or Europe, aircraft and ships often carry unauthorized passengers; stowaway mosquitoes.
Up until now, `Airport Malaria' has been the biggest concern, and the CDC even has a definition for it on their Malaria Transmission in the United States web page:
"Airport" Malaria"Airport" malaria refers to malaria caused by infected mosquitoes that are transported rapidly by aircraft from a malaria-endemic country to a non-endemic country. If the local conditions allow their survival, they can bite local residents who can thus acquire malaria without having traveled abroad
In 2008, the American Society of Tropical Medicine and Hygiene warned:
Warmer climate changes in major U.S. cities with a large presence of international air traffic, such as New York and Los Angeles, seem to have created a more welcoming environment where these infected mosquitoes can survive. It begins with a mosquito that is transported during an international flight from a malaria-endemic region. Once the infected female mosquito leaves the aircraft, it can survive long enough to seek blood meals and transmit the disease to other humans within the airport. This type of international transmission creates an increased possibility for the reintroduction of not just malaria, but other detrimental diseases such as dengue and Chikungunya fever, into areas where they are not normally found.
Today the UK has announced that all aircraft inbound from Zika endemic regions will be required to undergo disinsection, a procedure which is currently done for flights from regions where malarial diseases are endemic.
From: Department of Health, Department for Transport and Public Health England
All aircraft returning to the UK from countries currently affected by active Zika virus transmission will be sprayed with insecticide as part of a comprehensive government response to the disease.
On Monday, the World Health Organisation (WHO) declared the issue of microcephaly - which may be linked to Zika - a public health emergency of international concern.
As a precautionary measure, the government is asking airlines to ensure that disinsection (spraying with insecticide) takes place on all flights to the UK from countries with confirmed transmission of Zika.
Disinsection involves spraying a simple insecticide inside the aircraft to reduce the risk of passengers being bitten by any mosquitoes that could have entered the aircraft. It already occurs on the majority of flights from the region as a precaution against malaria.
The move is consistent with advice from WHO Europe. The type of mosquito that transmits the virus is extremely unlikely to survive and breed here given the lower temperatures in the UK.
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This practice, which is likely to become more common as Zika spreads, is not without its controversy. Although WHO weighed in on its safety 20 years ago (see below), some passengers have reported temporary ill effects or discomfort from the exposure.
The choice, however, is to either to spray flights or allow potentially infected mosquitoes free international travel, with complementary in-flight blood meals thrown in as a bonus.
The United States Transportation Department explains the procedures and the law:
Aircraft Disinsection Requirements
Disinsection is permitted under international law in order to protect public health, agriculture and the environment. The World Health Organization and the International Civil Aviation Organization stipulate two approaches for aircraft disinsection--either spray the aircraft cabin, with an aerosolized insecticide, while passengers are on board or treat the aircraft's interior surfaces with a residual insecticide (residual method) while passengers are not on board. Panama and American Samoa have adopted a third method, in which aircraft are sprayed with an aerosolized insecticide while passengers are not on board.
Although the Report of the Informal Consultation on Aircraft Disinsection sponsored by the World Health Organization (November 6-10, 1995) concluded that aircraft disinsection, if performed appropriately, would not present a risk to human health, the report also noted that some individuals may experience transient discomfort following aircraft disinsection by aerosol application.
Although few countries now require that aircraft be disinsected, most countries reserve the right to do so, and, as such, could impose a disinsection requirement should they perceive a threat to their public health, agriculture or environment. Accordingly, travelers are advised to check with their travel agent or airline reservations agent when booking flights. Listed below are representatives of airlines who are knowledgeable on disinsection requirements.
The UK appears to be the first major country to order the spraying of all flights from Zika affected regions, but other nations are no doubt considering similar steps.