Based on the analysis of publicly available data from CPHSD, the annual prevalence of HAV and HAV-related death rates in China have been decreasing. Morbidity and mortality vary by region and by age group. The morbidity rate was the highest among children and adolescents, and the mortality rate was the highest among middle-aged and elderly people (40–50 years old group). The highest morbidity rate was found in Sichuan and Xinjiang provinces. Although the incidence of hepatitis A is decreasing year by year (Fig. 1) (Table 1). However, due to China's vast territory, regional economic development is uneven. And it can be found from Fig. 2 that the areas with high HAV incidence are mainly concentrated in the west, while the population in the west of China is much smaller than that in the southeast. Relatively poor economic conditions and sanitary conditions may be one of the reasons for the high incidence of HAV in the western region (Sichuan, Xinjiang, Yunnan etc.).
The prevalence of HAV, especially in developing countries, remains a great challenge for the world's public health authorities.But, in this study, the year-on-year decrease in the prevalence of HAV and HAV-related mortality indicates that China's prevention and control measures have played a positive role. It is known that the prevalence of HAV is closely related to economic conditions and hygiene habits. For more than 10 years, with the development of China's economy, health and medical conditions have gradually improved, residents' awareness of disease prevention has increased, and the promotion of hepatitis A vaccine. These are probably the reasons why the fatality rate and infection rate in China have been declining year by year.
HAV is the most common pathogen that causes acute liver disease worldwide. In 2010, there were 1.4 million cases of hepatitis A and 27,731 deaths worldwide. The incidence of HAV widely between countries, with high prevalence in developing countries. It is also related to the quality of local sanitation, the quality of drinking water sanitation and socio-economic factors. In endemic areas, the severity of the disease is closely related to age. HAV infection mainly occurs in early childhood and, although mostly asymptomatic, can lead to illness and death in some cases. Symptomatic disease often occurs in older infected children and infected adults. For developed areas, due to health, medical care, high economic level, low prevalence. However, herd immunity is low and outbreaks are often reported.
HAV often causes symptomatic hepatitis in adults and asymptomatic subclinical infection in children. The incubation period for HAV is about 28 days. The clinical presentation usually occurs after the incubation period with sudden onset. Signs and symptoms of infection include nausea, vomiting, diarrhea, dark urine, jaundice, fever, headache, weight loss, abdominal pain, and loss of desire to smoke or drink alcohol. The likelihood of symptoms increases with age. Most children under the age of 6 have no symptoms. Jaundice can occur in more than 70 percent of older children and adults infected with HAV. Enlargement of the liver and spleen may occur. Acute illness from HAV infection usually lasts no more than two months. The clinical symptoms of HAV overlap with many other gastrointestinal and febrile symptoms, making it difficult to differentiate from other types of acute viral hepatitis.[16, 17]
Water-borne HAV infections are mainly due to drinking water contaminated by adjacent septic tanks or swimming in water contaminated with sewage.[18, 19] Food transmission mainly occurs when the faeces of HAV carriers are transferred to food during food preparation, or when the food plants are contaminated by the faeces of HAV carriers during harvesting or processing. Another modality of the faecal-oral route is extensive and close personal contact between the carrier and the vulnerable person. For example, MSM, in closed institutions such as schools and day-care attendance centers are susceptible to HAV by sharing items.[20, 21]
Therefore, the fecal-oral transmission of HAV can be effectively reduced in terms of daily diet, such as heating food and water to 85 degrees Celsius or above for one minute, avoiding contact with and eating uncooked food and natural water.[22, 23] In addition, prevention of vulnerable populations and children through active or passive immunization is the most important approach. Passive immunity: immunoglobulin. It can be used for pre-exposure prophylaxis or, in some cases, post-exposure prophylaxis. And according to the dose of different, in different time has a protective effect. Active immunization: Vaccines. The approval and widespread use of the 1990s HAV vaccine has paved the way for the prevention of this disease. The initial focus was on immunizing children in high prevalence areas and certain other high-risk groups.[25, 26] In 2006, the Centers for Disease Control and Prevention (CDC) made a major change, recommending HAV vaccination for all children between 12 and 23 months of age. In China, HAV vaccine has become one of the main vaccines for children and was included in the Expanded Immunization Vaccine for Children in May 2008.
As a developing country with a population of 1.4 billion, China faces great challenges in dealing with the spread of HAV. In 1988, an outbreak of hepatitis A sickened nearly 300,000 people in Shanghai, China, by eating raw clams, a popular delicacy that had been consumed by the city’s residents in the month before the outbreak began. With the improvement of economic level and the improvement of residents' environmental hygiene, as well as the widespread vaccination of HAV vaccine throughout the country, the reported incidence of hepatitis A decreased from > 50/100,000 in 1990 to 1.55/100,000 in 2017. Our study found that the incidence of HAV was regional and age specific, and the highest incidence of HAV was found in Xinjiang and Sichuan. The incidence is manifested by age in children, adolescents are vulnerable to infection transmission. The number of death cases showed a relatively high trend in the 40–50 years old group, which was significantly higher than the 20–30 years old group.
There are some limitations in this study. The coverage of data collection is not high enough to cover the entire HAV-infected population in China, and the lack of access to HAV epidemiological data in Taiwan, Hong Kong and Macau may lead to bias in this study. Also, the public data studies here are incomplete, making it impossible to analyze other risk factors such as race, occupation, residential environment and blood donation. This study focuses on regional and age differences in HAV in mainland China and concludes that HAV has regional and age characteristics. Regional attention needs to be paid to the spread of HAV in Sichuan and Xinjiang. Attention needs to be paid to transmission among children and adolescents. The public should be aware that more effective prevention strategies should be implemented to reduce and prevent the incidence of HAV/hepatitis A disease.