In 2005, an estimated 20.1 million people in Africa and Asia were infected with the hepatitis E virus (HEV), according to World Health Organization (WHO) data published in Hepatology and reported by Infection Control Today. The nine world regions covered by the study include 71 percent of the world’s population.

Unlike chronic hepatitis B and C infections, hepatitis E infection is acute, going away after several weeks. Symptoms include fever, fatigue, appetite loss, nausea, vomiting, dark urine and joint pain. Though the fatality rate is low, it can be very serious for some people. About 10 to 30 percent of pregnant women infected with the virus die of the acute disease, particularly when it occurs during the third trimester.

Genotypes 1 and 2, which are prevalent in Africa and Asia, affect only humans and generally appear in large outbreaks associated with contaminated food or water. Genotypes 3 and 4, which can infect pigs and other animals, were not included in the study.

While a hepatitis E vaccine exists and appears to be safe and effective, it is not in widespread use.

The WHO research showed that of the over 20 million people infected in 2005, about 3.4 million suffered symptoms of hepatitis E, with 70,000 deaths and 3,000 stillbirths. Compared with previous studies, the incidence rate increased most among young people ages 5 to 20. The average age of those infected with HEV was 17.

In addition, the impact of hepatitis E varied significantly by region. Specifically, 61 percent of infections and 65 percent of deaths were in East and South Asia, while North Africa had 14 percent of all cases but only 8 percent of deaths. The study authors suggest that this is connected to the relatively low average age of infection in North Africa—8 years old, the lowest of any of the nine regions studied. (The highest average age of infection was 21 years, in East Asia.)

“Our study represents the first attempt to estimate the annual global impact of hepatitis E,” said lead author David Rein, PhD. The authors noted that further study is required on the other two HEV genotypes, including genotype 3, the variant that’s most often encountered in the United States and Europe.