The patient, who has a weakened immune system after a kidney transplant, first tested positive in December 2020. Despite losing symptoms, he continued to test positive until January 2022. Doctors at Guy’s and St Thomas’ hospitals in London say they know of no other documented case of a person being cured after such a long infection. They used genetic analysis to determine that the unnamed 59-year-old still had an early variant of the original Wuhan strain — one that had long since been overtaken by Alpha, Delta and Omicron in general circulation. Only when they had identified the variant could they treat him with Regeneron, the same cocktail of drugs that helped Donald Trump fight the disease. The same group also treated a patient with an underlying condition who died after testing positive for 505 days. In both cases, genetic testing showed that the patients had not been reinfected. Cases of persistent infection differ from long-term COVID, where a patient may have symptoms for months or more but not be positive. Read more: Modeling predicts Christmas with low COVID – but another peak in January, Shanghai Disney Resort guests told to stay home after COVID outbreak The group treating the outbreaks has called for more research into antibody treatments for persistent cases of COVID, and campaigners have called for a new drug – Evusheld – to be made available in the UK and Europe. Dr Luke Blagdon Snell said: “Some new variants of the virus are resistant to all the antibody treatments available in the UK and Europe. “Some people with weakened immune systems are still at risk of serious illness and persistent infections. We are still working to understand how best to protect and treat them.” The team’s findings are published in the journal Clinical Infectious Diseases.