 Patients who satisfy all inclusion and none of the exclusion criteria will commence the treatment stage, which consists of one or more doses of CVA21 administered by intravenous infusion as per the dosage escalation chart. The first 4 cohorts will be treated as in-patients. The follow up period will consist of 12 weeks, during which time patients will attend the trial centre for up to13 follow up visits to collect safety and efficacy data. 