What is Zika virus? Symptoms of disease that affects babies, causes, and is there an outbreak

A single mutation to the Zika virus could make it a lot more infectious and dangerous, potentially triggering an explosive outbreak, researchers have warned.

The mosquito-borne virus caused a global emergency in 2016, causing thousands of babies to be born brain-damaged after their mothers were infected during pregnancy.

Lab experiments have identified a mutation that would make it even more contagious and virulent, with research suggesting the virus could easily shift, creating new variants, according to findings published in the journal Cell Reports.

Recent infection studies suggest that those variants could prove to be more effective at transmitting the virus, even in countries that have built up immunity against Zika from previous outbreaks.

Experts from the La Jolla Institute for Immunology in California say even though the findings were theoretical, it serves as a reminder that viruses other than Covid could also pose a significant health threat.

The researchers used mosquito cells and living mice in lab experiments to recreate what happens when the virus passes back and forth between mosquitoes and humans.

They found that small genetic changes occurred when Zika passed between mosquito cells and mice. This showed it was relatively easy for the virus to mutate in a way that allowed it to spread, even in animals that had some previous immunity from a similar mosquito-borne infection called dengue.

Lead investigator Prof Sujan Shresta explained: “The Zika variant that we identified had evolved to the point where the cross-protective immunity afforded by prior dengue infection was no longer effective in mice.

“Unfortunately for us, if this variant becomes prevalent, we may have the same issues in real life.”

What is Zika virus?

Zika virus is mainly spread by bites from infected mosquitoes found in some parts of the world.

It is most commonly found in parts of South and Central America, the Caribbean, the Pacific islands, Africa and Asia. The type of mosquitoes that carry Zika virus are not found in the UK.

It can also be sexually transmitted, although the NHS says this is very rare.

For most people it will be mild and not harmful, although it can cause problems for those who are pregnant, leading to the baby having an unusually small head (microcephaly) and damaged brain tissue.

Only one in five people infected with the virus are thought to develop symptoms, so it is important to avoid getting pregnant for up to three months after returning to the UK from a country where there is a risk of catching it.

What are the symptoms?

Most people will have few or no symptoms if they get Zika virus, with symptoms usually being mild in those who do and lasting for around two to seven days.

The most common symptoms include:

• a high temperature
• a headache
• sore, red eyes
• swollen joints and joint and muscle pain
• a rash and itching all over the body

If you have recently travelled to a country with a Zika virus risk, you should seek advice from a GP or call NHS 111 if any of the following apply:

• you feel unwell
• you or your partner are pregnant

• you or your partner get pregnant within three months of coming back to the UK
• you have numbness, pins and needles, muscle weakness or pain in your feet and hands that spreads to your arms and legs

Is there any treatment for Zika virus?

There are no specific treatments for Zika virus, but people who have symptoms are advised to get plenty of rest, drink lots of fluids and take pain relief, such as paracetamol.

If you are pregnant and have Zika virus, a midwife or hospital doctor will discuss the risk and may arrange an ultrasound scan to check the baby’s growth.

To minimise the risk of contracting the virus if you are travelling to an area where Zika is found, you should:

• use insect repellent on your skin – make sure it is 50% DEET-based
• sleep under mosquito nets treated with insecticide
• wear loose clothing that covers your arms and legs as mosquitoes that carry Zika virus are most active during the day