Spread of Zika virus
Sueli Maria (obscured) holds her daughter Milena, who has microcephaly, (born seven days ago), at a hospital in Recife, Brazil, January 28, 2016

Amid escalating fears of a global spread of the Zika virus, which has caused deformed brains in babies, New Zealand has said it has recorded nine new cases so far this year.

All the nine people contracted the mosquito-transmitted virus while travelling to South Pacific, the ministry of health said on Friday.

While four patients got the disease while travelling in Tonga, another four picked it up in Samoa, prompting the health ministry to include those countries in its travel advisory for New Zealanders.

"We will be providing advice to incoming travellers and the Ministry is updating its information for health professionals. There remains robust mosquito surveillance and monitoring at our borders," Don Mackie, chief medical officer at the ministry, said.

On Tuesday the World Health Organisation (WHO) said the level of alarm caused by the spread of the virus is extremely high. "The situation today is dramatically different. The level of alarm is extremely high," WHO chief Margaret Chan said.

She added that the outbreak this year has taken an unprecedented proportion.

As many as 21 countries in south and central America have reported the Zika virus infections, and the number is growing. In Brazil the virus has been linked to a foetal deformation known as microcephaly, in which infants are born with smaller-than-usual brains.

The country reported 3,893 suspected cases of microcephaly, the World Health Association (WHO) said last week.

"A causal relationship between Zika virus infection and birth malformations and neurological syndromes has not yet been established, but is strongly suspected," Chan said.

Vaccines are not available to counter the disease and there is no specific treatment for it. Meanwhile, scientists in the US, who likened Zika outbreak to the Ebola crisis, said it could be years before a vaccine is publicly available.

Zika virus facts

You get the disease when bitten by the infected Aedes mosquitoes.

Usually only one in five people infected with the virus gets sick.

According to WHO, the symptoms of Zika fever consist of mild fever, rash (mostly maculo-papular), headaches, arthralgia, myalgia, asthenia, and non-purulent conjunctivitis, occurring about three to twelve days after the mosquito vector bite.

Who are at risk? The US Centres fo Disease Control and Prevention has some useful infographics on regions especially vulnerable.

Most cases are mild but the disease develops complications in certain cases, especially in pregnant women and newborn babies.

In Singapore, medical experts have said the country is extremely vulnerable to Zika virus.

In southeast Asia, Cambodia and Thailand have reported Zika virus and the disease has historically occurred in southeast Asia.

The disease has spread to Europe with a Danish resident being diagnosed with the virus. The patient had traveled to Central and South America.

In Germany and Portugal too Zika virus has been found in people who returned from South America. As many as six cases have been reported in UK, Public Health England has said.