Curing pubic lice for three years usually does not recur and is considered a reinfection. It may be caused by environmental factors, indirect contact infection, sexual contact infection and other factors. 1. Environmental factors: if you are in a dark and humid environment for a long time and do not pay attention to hygiene and take a bath, you will be prone to pubic lice. You should adjust your living environment, keep the room clean, take a bath and change your underwear frequently. 2. Indirect contact: Sharing toiletries, bath towels, bed sheets, bedding, toilet seat, etc. with a person suffering from pubic lice may lead to the infection of pubic lice. 3. Reinfection: The presence of pubic lice disease in sexual partners and the lack of effective preventive measures during sex may lead to re-infection, which will lead to the recurrence of pubic lice disease. After the re-infection of pubic lice disease, you should seek medical examination and treatment as soon as possible to avoid delay.