The discovery that a mosquito species capable of transmitting the Zika, dengue and chikungunya viruses is breeding in east London may sound alarming, particularly to people living nearby. Yet finding the species is several steps removed from finding evidence that any of these viruses are circulating locally.

The UK Health Security Agency (UKHSA) has confirmed that Aedes aegypti mosquitoes and larvae have been found at residential properties in east London. This is the first recorded instance of the species breeding in the UK, although it is the fourth time the mosquito has been detected in Britain in recent years.

UKHSA considers the immediate risk to the public very low. It has found no evidence that the mosquitoes have caused human infections, and no mosquitoes or larvae have been detected in nearby public areas.

So what has happened, and what would have to change before these mosquitoes posed a significant threat?

From arrival to local transmission

Aedes aegypti, sometimes called the yellow fever mosquito, is a known vector of the Zika, dengue, chikungunya and yellow fever viruses. A vector is a living organism that can carry an infectious agent between people, or from animals to humans.

This mosquito is particularly well adapted to living near people. It often rests inside buildings, prefers to feed on humans, and lays its eggs........

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