-LRB- CNN -RRB- Spain is officially clear of Ebola, the World Health Organization declared Tuesday, after no new cases were reported since a nurse's assistant who contracted the virus there tested negative for it. Since then, 42 days have passed -- double the maximum known incubation period for the virus -- without another case, allowing Spain to be declared free of Ebola. Spanish authorities had been monitoring 87 people who came into contact with healthcare worker Teresa Romero Ramos, 15 of whom were considered high-risk and were quarantined at a Madrid hospital, WHO said. Another 145 hospital employees who helped care for Romero during her month-long stay at the Carlos III Hospital were also monitored. The WHO statement said it commends Spain for the measures put in place to identify potential cases and prevent further transmission of the Ebola virus. Romero contracted the illness while helping to care for an infected missionary who had been brought back from West Africa. He died of the disease. CNN's Anna Maja Rappard contributed to this report.