Pregnant women in Britain who have travelled to countries infected by the Zika virus have been advised to have an ultrasound to monitor their baby's growth.
The guidance from the NHS states women who were either pregnant when they travelled or who conceived within a fortnight of returning should see their GP even if they are feeling perfectly well.
The virus has been linked to a increase in the number of women in South America giving birth to babies with microcephaly – a condition causing an unborn baby's brain to stop growing in the womb.
"If you are pregnant and have a history of travel to a country where there is an ongoing Zika virus outbreak, see your GP or midwife and mention your travel history even if you have not been unwell," the advice on the NHS website states.
Doctors attend to a baby born with microcephaly in Brazil
The NHS advice continues: "Your midwife or hospital doctor will discuss the risk with you and will arrange an ultrasound scan of your baby to monitor growth.
"If you have experienced Zika symptoms either during or within two weeks of returning home, see your GP or midwife and mention your travel history.
"Your midwife or hospital doctor will discuss the risk with you and will arrange an ultrasound scan to measure your baby’s growth and brain development. If there are any problems you will be referred to a specialist fetal medicine service for further monitoring."
The World Health Organisation warned that the virus outbreak, which started in Brazil, is spreading so quickly that four million people could be infected by the end of the year.
Most people contract the virus through being bitten by an "aedes aegypti" mosquito. It cannot be caught from coming into contact with an infected person, however possible cases of sexual transmission have been reported.
There is currently no treatment or vaccine.
According to the Telegraph, six Britons are already known to have picked up the disease through mosquito bites while travelling in Columbia, Suriname, Mexico, the Cook Islands and Guyana.
The Foreign Office has advised women who are pregnant, or who are planning on becoming pregnant, to "Reconsider travel to areas where Zika virus (ZIKV) outbreaks are currently reported as further evidence for a possible link between ZIKV infection and congenital malformations emerges."
Elison, 10, nurses his 2-month-old brother Jose Wesley who was born with microcephaly following an outbreak of Zika virus in Brazil
Public Health England advised men to wear condoms during intercourse for 28 days after returning from Brazil, Mexico or any of the other countries where the virus has been detected, if their partner is pregnant or hoping to become pregnant.
The organisation advised: "If a female partner is at risk of getting pregnant, or is already pregnant, condom use is advised for a male traveller for 28 days after his return from a Zika transmission area if he had no symptoms of unexplained fever and rash.
"Condom use is advised for a male traveller for six months following recovery if a clinical illness compatible with Zika virus infection or laboratory confirmed Zika virus infection was reported."
A map illustrating the countries in the Americas where Zika virus outbreaks have been reported is available on the Pan American Health Organisation's website.
At the time of publishing, these included: Barbados, Bolivia, Brazil, Colombia, Costa Rica, Curaçao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Nicaragua, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, US Virgin Islands and Venezuela.