Footnotes

• Handling editor Tahir S Pillay.

• Contributors DP conceived the study. DN and PE provided expert advice about molecular biology. HO provided expert advice about virology. All authors reviewed and contributed to the manuscript. DP and RB wrote the manuscript.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Patient consent for publication Not required.

• Provenance and peer review Not commissioned; internally peer reviewed.