Brazil has declared an end to a national emergency over the Zika virus after a sharp decrease in cases. The number of cases dropped 95% between January and April, compared to the same period a year ago, officials said. The virus has been linked to the birth of babies with abnormally small heads. The threat was at its peak as Brazil prepared to host the 2016 Olympics. The World Health Organization lifted its own international emergency in November last year. The Zika virus has been linked to severe birth defects in almost 30 countries. Brazil had declared a national emergency in November 2015. The threat led to a campaign to eradicate the mosquitoes which carry the virus. There were 7,911 cases of Zika from January to April this year, compared to 170,535 cases reported in the same time last year, the health ministry said in a statement (in Portuguese). No deaths related to the virus have been reported this year, it added, saying that eight people died last year.