Health officials at London's Heathrow Airport have begun screening travelers from West Africa for Ebola.<br /> <br />But passenger Clive Paterson, who's been making a film about Ebola in Liberia, says he's surprised it's not compulsory.<br /> <br />(SOUNDBITE) (English) DOCUMENTARY MAKER, CLIVE PATERSON, SAYING:<br /> <br />"I would've thought if you're coming from a country like Liberia that you just have to be screened. It just seems to make more sense if you're going to go to this effort anyway."<br /> <br />The current outbreak of the virus is the worst on record and has already killed more than 4,000 people -- mostly in Liberia, Sierra Leone and Guinea.<br /> <br />Some have raised doubts about the effectiveness of border screening, since an infected person may not immediately show symptoms.<br /> <br />But Paul Cosford, who's the director of Public Health England, says he believes it will help.<br /> <br />(SOUNDBITE) (English) DIRECTOR OF PUBLIC HEALTH ENGLAND, PAUL COSFORD, SAYING:<br /> <br />"Obviously, this is a very new
