The Zika pregnancy cases have doubled in Colombia in just one week, officials said.

According to Colombia’s National Health Institute, almost 2,000 pregnant women now have the virus out of the more than 20,000 people infected across the country.

The mosquito-borne virus has been linked to babies being born with abnormally small brains.

The World Health Organization (WHO) has warned Zika is “spreading explosively”, predicting up to 4 million cases this year.

Colombia says it expects the overall number of people to be infected to rise to more than 500,000 by the end of 2016.

On February 1, the WHO meets to decide whether Zika should be treated as a global emergency.

Brazil has been worst affected by the outbreak, followed by Colombia, but more than 20 other countries have seen cases.

Jamaica and Peru reported their first confirmed cases over the weekend, with Peruvian President Ollanta Humala urging calm and stressing that the patient contracted the disease outside of the country.

Zika symptoms are mild, causing a low fever, joint pain, headaches, a rash and conjunctivitis.

Concern surrounds a surge in babies born with microcephaly, or abnormally small heads, from mothers infected with Zika. A link has not been confirmed.

Colombia has also said it has seen an increase in cases of Guillain-Barre syndrome, a rare disorder that can cause temporary paralysis, that has also been linked to Zika.

The Zika outbreak has sparked health warnings and eradication campaigns, with Brazil deploying troops and Colombia launching a mass fumigation campaign to fight mosquitoes.

Colombia and other Latin American countries have advised women to delay getting pregnant for the moment.