Will Zika Keep Spreading?

Zika has spread to most countries in the Western Hemisphere

Will Zika spread everywhere?


But Zika has recently spread to a number of countries.

Yes, it has spread to a number of countries. These include: - but are not limited to

Brazil, Antigua, Aruba, Barbuda, Barbados, Bolivia, Colombia, Costa Rica, Cuba, Curacao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Nicaragua, Panama, Paraguay, Saint Martin, Suriname, Trinidad and Tobago, Turks & Caicos, Venezuela, Puerto Rico.

It has also been seen in Cape Verde, American Samoa, Samoa, Guinea-Bissau, Singapore, and Tonga.

Why not more?

Well, it will spread to some more, but it won’t spread everywhere in the world. One of the big questions is whether southern Texas and Florida will see cases.

Mosquitoes aren’t everywhere

Zika spreads by mosquitoes. But not just any mosquitoes. Zika has traditionally spread by Aedes aegypti. It seems also that Aedes albopictus spreads the virus. There may be some other mosquitoes as well.

But it doesn’t seem like any old mosquito can spread Zika. This is good news for most in the US, Canada, and Europe. Not as good news for people who live in warm climes.

Can’t the mosquitoes spread?

No, it’s cold. It’s not expected that Zika will spread to Chile or Canada ever. Wrong climate, no Aedes mosquitoes.

There are Aedes aegypti mosquitoes in Florida, Texas, and southern California. The mosquitoes have also been found in areas of Arizona, Alabama, Georgia, South Carolina, Mississippi, and in limited parts of surrounding states.

Likewise, Europe has almost no Aedes aegypti mosquitoes. There are some in southern Russian along the Black Sea.

Aedes albopictus has been spreading within the US since the 1980’s. It reaches over a wide region from Texas and throughout the South down to Florida and up to New Jersey, Indiana, and Illinois, as well as in Arizona and Hawaii and pockets in other states.

Likewise, most of Europe does not have Aedes albopictus. Italy as well as Mediterranean France, Spain do have the mosquitoes. Greece, Albania, and islands within the Mediterranean (Sardinia, Sicily, Corsica) also have Aedes albopictus.

Aedes albopictus has also been spreading in Africa after arriving from Asia. In areas throughout Africa and Asia that see Dengue, Chikungunya, or Yellow Fever, there are Aedes mosquitoes that are capable of spreading Zika (and may have already in the past).

Mosquitoes don’t always lead to mosquito-borne viruses

These mosquitoes are not as numerous as they are in many hard hit Zika areas.

Although present, the mosquitoes have in many areas, such as in the US or Europe, not led to outbreaks of viruses that have been circling globe. Dengue (4 strains or subtypes) and Chikungunya have not caused major outbreaks in Europe or most of the US in recent times. Historically, the US saw outbreaks of Dengue (and possibly Chikungunya) from Charleston, SC to Philadelphia, PA to Galveston, TX.

Hawaii, which has Aedes albopictus, had an outbreak of dengue this past year. Southern Florida and Southern Texas have seen occasional local transmission of Dengue. There are more regular outbreaks in Puerto Rico, the US Virgin Islands, Samoa, and Guam.

Europe has also seen small outbreaks from Aedes mosquito-borne viruses. France and Italy have seen Chikungunya spread locally – but to a limited extent. The Portuguese Madeira islands had an outbreak of Dengue recently.

Mosquito control is an important and continues to be an important element in avoiding these mosquitoes. Where the climate is even nicer to the mosquitoes and water spots (where the mosquitoes breed) are plentiful, there can be even more infections.

But Zika may be an STD?

Yes, Zika is also spread through sexual contact. The virus has been found in semen. It has also been shown to spread from women to men.

It is unknown for how long after infection that someone is infectious. Since most cases of Zika cause no symptoms, it is also not known whether someone who doesn’t know that they had Zika can be infectious.

Spread of Zika as an STD is expected to be much less frequent than by mosquitoes, which are the primary means of transmission. The risk of Zika as an STD appears to only affect people who have sex with men, who have had Zika or who have returned from affected areas. It is not thought to be a virus that persists for a long time and the risk may only last for a short time.

What about outside of Europe and the Western Hemisphere?

Some places have already had it. Much of Africa has likely had a history of Zika. However, some places, like Uganda may have had the virus - but not in humans. The virus may remain in other animals, like monkeys, that don't have contact with people - nor do their mosquitoes have contact with people.

Parts of Asia have long had evidence Zika. In fact, a patient from Thailand was diagnosed recently in Taiwan. The history of past infection may buffer areas against the explosive spread of Zika in a population that is not immune, as Brazil saw.

There are places in Europe and Africa that have not had Zika.There may be other areas in Africa and Asia that are vulnerable and have not had so many infections before.

In Africa, in 2007, Gabon had an outbreak of Zika. There are other countries in Asia which likely have not had Zika. Japan usually does not have Dengue, but had an outbreak of Dengue in 2014.

However, it is not expected that Canada, the US, or much of Europe will face any large outbreaks (and Canada and Northern Europe should be free entirely)

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