Government restrictions on international travel have tightened again in the UK as a surge in new infections linked to the emergence of virus variants threatens the airline industry’s summer recovery. The UK recently removed Portugal from the ‘green’ list of the government’s traffic light system for quarantine-free travel. The decision follows a spike in Portugal’s infection rate, which currently exceeds the rate in the UK according to the Office for National Statistics (ONS). More significantly, 77 cases of the ‘Delta’ variant of Covid-19 were reported according to data published on GISAID. The Delta variant, first identified in India, carries the risk of a potentially detrimental mutation, while the efficiency of existing vaccines against this variant is not yet determined. Public Health England (PHE) has begun an investigation.