Kerala has now strengthened screening measures at airports examining over 450 passengers who landed from African countries. No one has yet been tested positive for Ebola in the state. Airports will be soon extending the screening to sea ports also in order to check possible threat of its spread in the state State Health Secretary K Elangovan said. 'No Ebola positive case has been reported so far in the state. We have already taken strict measures to monitor the situation and stepped up screening at the airports. We are now mulling extending similar checks at seaports also' he told PTI.