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In the late summer of 1999, there was an epidemic of encephalitis and meningitis in New York. To begin with, all the sufferers came from an eight square kilometer area centered on Queens and the Bronx.

Later, it spread further, although there were merely 59 cases and seven deaths - all in older individuals. 677 individuals were tested in the original survey, 19 of which tested positive for meningoencephalitis.

Going by the size of the population of New York, it was determined that between 3,500 and 13,000 people (average: 8,200) had been infected with West Nile virus. There were almost certainly far more than that, but serious indications usually only show in the young and the old.

Those in the in-between age group probably reckoned that they had a bad cold, which means that fewer than one percent of sufferers displayed severe neurological symptoms.

At first, it was considered whether this outbreak could be the result of an act of terrorism, but others suspected mosquitoes. Investigation concentrated on St. Louis encephalitis. However, when it was thought to test for West Nile virus, the number of cases increased.

The cause of the epidemic was soon confirmed to be a West Nile-like virus based on the identification of viral infection in human, avian, and mosquito samples.

This had not been expected because the New York outbreak was the first time that West Nile virus had been seen in the Developed world.

Then recent bird deaths were remembered. Large numbers of wild birds, especially crows, had died recently in the region and there were deaths at the Bronx Zoo of exotic birds as well.

Examination of the corpses of these birds showed traces of encephalitis which resembled West Nile virus (WNV). When doctors knew what to look for, they discovered comparable traits in the brains of the dead humans

The authorities immediately initiated widespread measures to control the numbers of Culex pipiens, the mosquito in the region that specializes in attacking birds. The public was informed and helplines were set up - by the end of September over 150,000 calls had been made.

The local authorities continued to spray and handed out 300,000 aerosols of DEET and 750,000 public health leaflets, which recommended tidying up the garden, not going out at dusk or dawn and covering up bare skin.

WNV is an arbovirus (arthropod-borne virus), which means that it is transmitted to humans by arthropods (insects), normally the tick or the mosquito. Previously, WNV had only been seen in Uganda, where it was first discovered and in isolated cases in Europe and South Africa.

A report concluded that it was “unclear whether the virus that caused this outbreak is a previously identified strain of WNV or a new variant”, however now recent evidence seems to suggest that a new mosquito - a hybrid of C. pipiens - living in the New York metro was to blame.

This is still not definite, but if it is the case, then the whole world ought to take care, because the New York ‘hybrid’ is related to the London Underground mosquito which inhabits nearly every underground railway station on the planet.

Owen Jones, the writer of this article writes on a number of topics, but is currently involved with finding a home remededy for mosquito bites. If you would like to know more, please go to our web site at Getting Rid of Mosquito Bites.

Who would have thought that the London Underground is home to a unique species of mosquito? The species is called the London Underground mosquito and is considered to have evolved from Culex pipiens. The London Underground species has been dubbed Culex pipiens molestus, because it is a vigorous biter.

It is not new, but it is comparatively new in biological terms. Molestus is known to have bitten Londoners during the Second World War whilst they were taking refuge during the air raids. However, there are other references to a mosquito with the same name, molestus, 170 years before the war, when there was no underground railway system in London or anywhere else in the world.

This mosquito was first discovered in the London Underground, which is why it got its name, but it can be discovered in metro and underground railway systems all around the world. No one really knows much concerning this insect population yet.

Some individuals suggest that it is a variant of a local Culex pipiens that has adapted to living in warmer, underground tunnels, while others say that is a southern (and therefore warmer) variant of C. pipiens that is able to live in the colder north because it has inhabited the warm train tunnels of the underground railways.

Yet others, notably Kate Byrne and Richard Nichols, propose that it is a totally different species from Culex pipiens. Their evidence for saying this is that there are differences between pipiens and molestus: they display very different behavioural patterns and do not mate readily with each other.

C. pipiens molestus will bite rats, mice and humans and dies in cold temperatures but remains active all year round, whereas C. pipiens can tolerate cold weather, just bites birds and hibernates if the weather gets very cold.

On the rare occasions when the two varieties cross breed, the eggs are infertile, which suggests that they are distantly related if at all. Recent studies indicate that molestus originated in one source but spread rapidly around the world, maybe in freight.

Second-hand tyres have been held responsible for spreading molestus throughout the world. There is a colossal international trade in second hand tyres and it is notoriously problematic to get all the water out of a tyre that has been left in the rain. Mosquitoes can breed in a tiny amount of water, so this is a possibility.

There is a strange and not entirely explained twist to the story of the molestus, the American version of molestus pipiens still bites birds which leads some people to suggest that molestus is a separate species, but that it has become a hybrid in America with pipiens.

This is fairly frightening, but fairly possible, because the American pipiens can transmit human encephalitis brought about by the West Nile virus, an outbreak of which hit New York in 1999.

There is a lot more to find out about the London Underground mosquito, since the story is only just beginning to unfold. The real story will probably come out of America where this new mosquito has proved to be the most dangerous.

Owen Jones, the author of this piece writes on several subjects, but is currently involved with finding a home remededy for mosquito bites. If you would like to know more, please go to our website at Getting Rid of Mosquito Bites.