News comes as a global state of emergency over virus has been declared

Ireland's health service says the cases are 'not an unexpected event

The cases are unrelated to each other and patients are fully recovered

Two adults have been confirmed with the Zika virus in Ireland, health chiefs have said.

The cases - the first of their kind in the country - are unrelated to each other and both patients are said to be currently well and fully recovered.

Both individuals have a history of travel to a Zika affected country, Ireland's Health Service Executive (HSE) confirmed.

City workers are shown fumigating the Jardines de Merliot neighbourhood as part of preventive measures against the Zika virus and other mosquito-borne diseases in Santa Tecla, El Salvador

'These are the first cases of Zika virus infection confirmed in Ireland,' a HSE spokeswoman said.

'Neither case is at risk of pregnancy.'

The HSE said the newly-discovered Zika cases in Ireland are 'not an unexpected event' as many other European countries have reported cases as a result of people travelling to affected areas.

Health chiefs have urged Irish people who fall ill within two weeks after returning from an affected area to seek medical help.

The news comes as the first known case of the Zika virus being sexually transmitted in the United States has been reported.

The US Centers for Disease Control and Prevention said a patient in Texas had been infected with the virus after having sexual contact with an ill person who returned from a Zika-affected country.

The virus is usually spread through mosquito bites, but investigators have been exploring the possibility it can also be spread through sex.

The virus was found in one man's semen in Tahiti, and there was a report of a Colorado researcher who caught the virus overseas and apparently spread it to his wife back home in 2008.

The virus is usually spread through mosquito bites, but investigators have been exploring the possibility it can also be spread through sex

Last week, Public Health England warned men in the UK to wear condoms for a month after returning from any of the 23 countries affected by Zika.

In guidance the body said: 'Sexual transmission of Zika virus has been recorded in a limited number of cases, and the risk of sexual transmission of Zika virus is thought to be very low.

'However, if a female partner is at risk of getting pregnant, or is already pregnant, condom use is advised for a male traveller.'

Ministers have insisted the risk posed by the spread of the mosquito-borne Zika virus to the British public remains 'extremely low'.

The World Health Organisation (WHO) has declared an international emergency over the virus, which is linked to birth defects in Brazil and the Americas.

The virus, which is commonly found in parts of Africa and South East Asia spread to Latin America via French Polynesia. Last year more than 1.5 million people in South America became infected, before the virus jumped to the Caribbean, Mexico and Texas towards the end of 2015

The virus, which is commonly found in parts of Africa and South East Asia spread to Latin America via French Polynesia. Last year more than 1.5 million people in South America became infected, before the virus jumped to the Caribbean, Mexico and Texas towards the end of 2015

Professor Uriel Kitron, of Emory University and an expert in vector-borne diseases, which are transmitted by mosquitoes, ticks and other organisms, said: 'This is a huge public health emergency and horrible on many levels.

'The microcephaly cases are a personal tragedy for the families whose babies are affected.

'They will need much care and support, some of them for decades.

'The costs to the public health system will be enormous, and Brazil was already experiencing an economic crisis.'

For the past several years, Professor Kitron has collaborated with Brazilian scientists and health officials to study the dengue virus, which is spread by the same mosquito species, Aedes aegypti, as Zika.

The focus of that collaboration is now shifting to Zika.

Professor Kitron will return to Salvador, the capital of the Brazilian state of Bahia, this month to support the country's research strategies and control efforts for the outbreak.

'Dengue is a very serious disease, but it doesn't usually kill people,' he said.

'Zika is a game-changer. It appears that this virus may pass through a woman's placenta and impact her unborn child. That's about as scary as it gets.'

ZIKA FACT BOX How do people become infected? The virus is transmitted to people through the bite of infected female Aedes mosquitoes, the same type of mosquito that spreads dengue, chikungunya and yellow fever. The Pan American Health Organization (PAHO) said Aedes mosquitoes are found in all countries in the Americas except Canada and continental Chile, and the virus will likely reach all countries and territories of the region where Aedes mosquitoes are found. How do you treat Zika infection? There is no treatment or vaccine available for Zika infection. Companies and scientists are racing to develop a safe and effective vaccine for Zika, but one is not expected to be ready for months or years. How dangerous is it? The PAHO said there is no evidence that Zika can cause death, but some cases have been reported with more serious complications in patients with pre-existing medical conditions. The virus has been linked to microcephaly, a condition in newborns marked by abnormally small heads and brains that have not developed properly. It also has been associated with Guillain-Barre syndrome, a rare disorder in which the body's immune system attacks part of the nervous system. Scientists are studying whether there is a causal link between Zika and these two disorders. How is Zika related to microcephaly? Health officials have yet to establish a direct causal relationship between Zika virus infection and birth defects, but it is strongly suspected. Brazil has reported 3,700 cases of suspected microcephaly that may be linked to Zika. It is unclear whether in pregnant women the virus crosses the placenta and causes microcephaly. Research in Brazil indicates the greatest microcephaly risk appears to be associated with infection during the first trimester of pregnancy. What are the symptoms of Zika infection? People who get Zika virus disease typically have a mild fever, skin rash, conjunctivitis, muscle and joint pain and fatigue that can last for two to seven days. But as many as 80 percent of people infected never develop symptoms. The symptoms are similar to those of dengue or chikungunya, which are transmitted by the same type of mosquito. Advertisement

Since the Zika outbreak began in northeastern Brazil last spring, an estimated 500,000 to 1.5 million people have been infected.

The resulting illness only lasts a few days. The symptoms, including a rash, joint pains, inflammation of the eyes and fever, tend to be less debilitating than those of dengue.

As many as 80 per cent of infected people may be asymptomatic.

It was not until months after Zika cases showed up in Brazil that a spike in microcephaly births was tied to women infected during pregnancy.

More than 3,500 microcephaly cases have been reported since October in Brazil, compared to around 150 cases in 2014.

While Zika's connection to microcephaly - a congenital malformation by which babies have abnormally small heads and may suffer from delayed brain development - has yet to be definitively proven, the presence of the virus has been found in the bodies of five of the newborns that died with the condition and in the placentas of two women who miscarried babies with microcephaly.

The Centers for Disease Control and Prevention has warned pregnant women not to travel unnecessarily to countries currently experiencing an outbreak of Zika virus.

The Zika virus is thought to be connected to birth defects if it is caught by pregnant women

Zika's connection to microcephaly - a congenital malformation by which babies have abnormally small heads and may suffer from delayed brain development - has yet to be definitively proven

But the presence of the virus has been found in the bodies of five of the newborns that died with the condition and in the placentas of two women who miscarried babies with microcephaly

The governments of Brazil, El Salvador and Columbia, meanwhile, are urging women to delay any plans of pregnancy.

'People are worried that Zika may also have other, more subtle, effects on fetuses besides microcephaly,' Professor Kitron said.

'We just don't know that much about Zika. It has not been studied extensively in the lab and field data is also limited.'

It was not until months after Zika cases showed up in Brazil that a spike in microcephaly births was tied to women infected during pregnancy. More than 3,500 microcephaly cases have been reported since October in Brazil, compared to around 150 cases in 2014

The Zika virus is named after an isolated forest in Uganda where it was discovered in a monkey in 1947.

Only a handful of human cases were known until 2007 when it popped up in the Yap Islands of the southwestern Pacific Ocean, sickening thousands of people.

In 2013 Zika appeared in French Polynesia and the following year in other islands of the South Pacific.

Brazilian soldiers are shown conducting an inspection for the Aedes aegypti mosquito on a street in Recife, Brazil, this month. Health authorities in the Brazilian state at the center of a rapidly spreading Zika outbreak have been overwhelmed by the alarming surge in cases of babies born with microcephaly, a neurological disorder

Although Zika outbreaks have coincided with a slightly increased rate of Guillan-Barre's Syndrome, none of the previous outbreaks were associated with a spike in microcephaly births.

The Brazilian Zika outbreak, first identified in May, is the largest ever.

The cases are centered in the northeastern states of Paraiba, Pernambuco and Bahia.

Zika quickly spread in the region, since the population had never been exposed to the virus, making it highly susceptible.

Given the high rate of infection, herd immunity may delay future outbreaks for several years, Professor Kitron said.

Zika cases were initially confused with chikungunya, another virus transmitted by the Aedes aegypti mosquito that was introduced to Brazil and other parts of Latin America and the Caribbean in 2014.

Zika, chikungunya and dengue viruses are all now circulating in Brazil.

They cause similar symptoms, complicating clinical identification during outbreaks.

And no treatments or vaccines exist for any of the three viruses, making mosquito control vital.

'Mosquito control is not considered 'sexy' science, like developing a new drug or a vaccine,' said Professor Kitron, 'but more attention and resources need to be devoted to it.'

WHO director-general Dr Margaret Chan declared the Zika outbreak a public health emergency, calling for a coordinated international response to the crisis, to minimize the impact in affected nations and stop its spread

Aedes aegypti are like 'the roaches' of the mosquito world, perfectly adapted to living with humans, especially in urban environments, said Gonzalo Vazquez-Prokopec, another disease ecologist in Emory's Department of Environmental Sciences who studies vector-borne diseases.

Vazquez-Prokopec specializes in spatial analysis of disease transmission patterns and has several research projects for dengue fever ongoing in Latin America.

He is traveling to the Brazilian capital of Brasilia this month to assist the country's vector control team as they continue to battle the outbreak through mosquito control.

While mosquitoes that carry malaria only feed during the evening, the Aedes aegypti feeds almost exclusively on humans and bites primarily during the daytime.

'Killing mosquitoes is labor-intensive and expensive if you do it well, and it can be difficult to get funding for it,' Vazquez-Prokopec said.