In China, a more extensive population ALT screening was conducted in the 1960s, and asymptomatic elevated serum ALT accounted for about 5-10% of the population. After the development of HBsAg testing, it was found that the detection rate of HBsAg was three times higher in those with abnormal ALT than in those with normal, and nearly half of those with elevated single ALT were hepatitis B without xanthogranuloma. So how can elevated single alt be prevented? Here is a look together. 1, pay attention to daily life diet: viral hepatitis can be prevented. The focus of prevention should be should be on improving the level of health of the whole society, focusing on diet, water and personal hygiene to develop before meals, wash hands after going out and return to wash hands, do not eat unclean food, do not drink raw water. Secondly, we should strengthen hospital disinfection and isolation, and medical equipment should be strictly disinfected, so as to interrupt the medical source of transmission. 2, timely injection after contact with patients: after contact with hepatitis B patients timely injection of a shot of hepatitis B high efficiency immunoglobulin, 2-4 weeks after the first injection of hepatitis B vaccine, in 1 month and 6 months and then injected 2-3 shots of hepatitis B vaccine, ill contact with hepatitis A patients, within 2 weeks, intramuscular injection of gammaglobulin containing anti-hepatitis A antibodies. 3, isolate the contact: the pediatric contact with a hepatitis patient can be passed to another person, so that the disease will spread one by one, more and more, resulting in an epidemic. To prevent this from happening, it is necessary to isolate and observe contacts until the end of the incubation period.