For the second time in history, scientists believe that they have cured a patient of HIV. The key to this possible cure is a gene known as CCR5. Some people have a mutation of this gene that is resistant to HIV.

The patient, who is known to come from London, had HIV and a rare form of blood cancer. He got a stem cell transplant to treat the cancer from a donor who has the HIV-resistant form of the gene. The transplant helped treat both the cancer and the HIV. The patient has been in HIV remission for 30 months.

The success of the treatment is groundbreaking; however, scientists warn that the gene treatment should only be used as the last option for patients who also have blood cancer.

Difficult words: mutation (the change that happens in genes and that is passed to new organisms when they reproduce), stem cell (a cell that has the ability to develop into many different cell types), remission (a period of time when an illness is less severe or not affecting someone).