An increase in hepatitis A infections in a Chinese province earlier this year has been attributed to eating raw or undercooked seafood.

In February 2020, there was a 138 percent increase in hepatitis A infections reported to the National Notifiable Disease Report System (NNDRS) from Liaoning Province compared with February 2019, and more than three quarters of cases in Liaoning were from two coastal cities — Dalian and Dandong. These cities are on the Liaodong Peninsula wher seafood is abundant. From November to April, many types of fresh seafood are sold and consumed by residents, and most eat raw seafood.

All cases were sporadic. Through a survey of affected people and a case-control study, researchers found that consuming raw or undercooked seafood, clams, snapping shrimp, and oysters was significantly associated with the increase. Findings were published in China CDC Weekly.

Local governments took measures including health education, restricting sale of seafood products in markets, messaging on avoiding consuming raw seafood and an encouragement of Hepatitis vaccination. For a week in mid-March, the Chinese Center for Disease Control and Prevention (CDC), Liaoning Provincial CDC, and Dalian and Dandong CDCs jointly investigated and identified consumption of raw seafood as the main risk factor associated with the Hepatitis A rise.

Investigating uptick
Hepatitis A cases reported from Liaoning Province in January through mid-March increased from 700 in 2019 to 1,361 in 2020, accounting for one-third of all cases nationwide.

There were 426 and 586 cases reported from Dalian and Dandong, which accounted for 1,012 of all 1,361 cases from Liaoning. Zhuanghe County of Dalian and Donggang County of Dandong reported 262 of 426 and 290 of 586 cases, which was more than any other county. By mid-March 14, 4,418 adults in Zhuanghe County of Dalian and 1,861 people in Donggang County of Dandong were vaccinated.

Most were among adults aged 30 to 54 years old in Dalian and 30 to 49 years old in Dandong. There were four reported cases among children less than 15 years of age, and three of them had no history of HAV vaccination. By occupation, half were farmers and under a third were among household workers or unemployed individuals.

Interviews by local CDCs focused on five themes including eating habits, drinking water, types of seafood eaten, dining-out behavior, and sources of food during their incubation period.

Researchers analyzed data from case interviews between January and early March in Zhuanghe County and found that 104 of 146, 31 of 84, and two of 15 interview subjects who consumed oysters, snapping shrimp, or cockles ate them raw. During the same time in Dandong, the percentage of hepatitis A cases with a history of seafood consumption in 2020 was 84.7 percent, or 287 of 339, which was higher than in 2018 and 2019.

The case-control study involved 191 confirmed Hepatitis A cases reported between January and the first week of March in Zhuanghe County and 277 healthy individuals living in the same county were the control group. Consumption of raw or undercooked seafood, eating clams, snapping shrimp and oysters were significantly associated with HAV infection.

Mitigation measures
Hepatitis A case reports began to increase in December 2019, one month after local seafood became available in November. Following a sharp rise in seafood sales during Spring Festival in January 2020, there was a peak of cases in February and early March, according to the study.

In March, 30 samples of seafood were collected from local markets; 23 of seafood from coastal areas, and three of water from the Yellow Sea estuary. All were negative for Hepatitis A virus (HAV). The low sensitivity of the real-time RT-PCR approach and the delay between illness onset and sample collection could explain the lack of HAV-positive samples.

Researchers suggested strengthening health education of residents to avoid eating raw or undercooked seafood, encouraging HAV vaccination of adults aged 20 to 54 to prevent periodic HAV endemic outbreaks, restarting routine immunization and catching up of children who missed vaccinations due to the COVID-19 pandemic, and Hepatitis A surveillance in areas with a high prevalence of infections to monitor HAV and its genotypes in patients, the environment, and food to provide data for updating prevention and control strategies.

“Our study found that consumption of seafood before Hepatitis A onset was higher than in previous years and that consumption of raw or undercooked seafood were significantly associated with HAV infection. Clams and oysters have been shown to be frequently contaminated with HAV, making Hepatitis A outbreaks caused by raw seafood consumption common.”

Recognizing World Hepatitis Day
World Hepatitis Day is marked each year on July 28 to enhance awareness of viral hepatitis, an inflammation of the liver that causes health problems, including liver cancer. There are five main strains of the virus – A, B, C, D and E.

Hepatitis A is spread when someone ingests the virus through close contact with an infected person or by eating contaminated food or drink. The incubation period is usually 14 to 28 days. Symptoms can last up to two months and include fatigue, nausea, stomach pain, and jaundice. Most people do not have long-lasting illness. The best way to prevent it is to get vaccinated.

Hepatitis E is a liver infection caused by the hepatitis E virus (HEV) that is spread when someone ingests the virus. In developing countries, people most often get it from drinking water contaminated by feces from those who are infected. In the United States and other developed nations wher hepatitis E is not common, people have gotten sick after eating raw or undercooked pork, venison, wild boar meat, or shellfish.

Symptoms can include fatigue, poor appetite, stomach pain, nausea, and jaundice and usually last from one to six weeks. However, many people, especially young children, have no symptoms. The incubation period following exposure to HEV ranges from two to 10 weeks, with an average of five to six weeks. Most people recover fully without any complications. No vaccine for hepatitis E is currently available in the U.S.