The likelihood of Victorians being kept in their choking lockdown for a second week - or longer - will not depend on the number of new cases, but whether they are linked to already known cases or from mystery sources. The number of cases in the state rose to 51 on Monday after 11 new local infections were confirmed. Contact tracers are scrambling to identify about 4,200 close contacts and 279 exposure sites as the end of lockdown looms on Thursday. Victoria's chief health officer Brett Sutton described the virus as 'an absolute beast' and that authorities were 'neck and neck' with it in the fight to trace cases and control its spread by Friday, or concede defeat and go for another long, hard lockdown.