following the world health organization suggested it could defeat ebola by the end of the year and margaret chan during a briefing with the u.n. security council but she also warned that just one new case can ignite a flare-up, the deadly disease erupted in africa last year and effected 30,000 people and killed more than 11,000. >> if the current intensity of case action and contact tracing is sustained, the virus can be defeated by the end of this year. that means going to zero and staying at zero. >> reporter: the world health organization spoke us to earlier saying predictions are not premature but all groups on the ground need to be vigilant. >> it is very, very important that we do not get complacent. together with the population and together with turkey and all those who have been involved in the response so far, we have seen that one unsafe burial can lead to a number of new transmission chains so we have to be vigilant, what we got from the first trial and it seems that the vaccine is safe, efficient, again, further studies are needed and need more research to be really absolutely sure t