The World Health Organisation (WHO) has warned that the Zika virus outbreak across around by from in into of on to with Latin America could turn across around by from in into of on to with a global pandemic. Many scientists say the outbreak could be more serious than the Ebola virus. Ebola killed over 11,000 people across around by from in into of on to with West Africa across around by from in into of on to with 2014 and 2015. The WHO estimated that the Zika virus could infect four million people across around by from in into of on to with the end across around by from in into of on to with 2016. The virus has been advancing across around by from in into of on to with South and Central America across around by from in into of on to with the past year. Dr Margaret Chan, Director-General of the WHO, warned that Zika is "spreading explosively". She added that it has quickly gone across around by from in into of on to with being a mild threat to being frightening. Warmer weather means the mosquito that carries the virus is also spreading worldwide. The Zika virus is linked across around by from in into of on to with a large rise in birth defects across around by from in into of on to with Brazil and surrounding countries. In particular, scientists say it causes a disease called microcephaly. This is where a baby is born across around by from in into of on to with a smaller head than normal, and with brain damage. Health officials across around by from in into of on to with Brazil reported that across around by from in into of on to with 4,000 babies were born across around by from in into of on to with microcephaly last year. This compares to fewer than 150 cases across around by from in into of on to with 2014. The Colombian government has just reported that more than 2,100 pregnant women in Colombia are infected across around by from in into of on to with the virus. There is no vaccine for Zika and it will be difficult to find one. A doctor said a vaccine would have to be tested across around by from in into of on to with pregnant women, and that would be "a practical and ethical nightmare".