Traveler's Infections: Overview of Hepatitis B Virus Infection

*Victor B. Oti*

## **Abstract**

Hepatitis B virus (HBV) is a double-stranded circular DNA virus that infects the hepatocytes. HBV infection is considered as an important public health concern globally especially with one-third of the world's population been infected. Local and international migrants are one of those population at high risk of the infection. Many factors interplay in the acquisition of HBV such as purpose of travel, destination endemicity rate of the virus, time of stay of the traveler, inadequate prevention and control measures, among others, understanding the genotypes of HBV is critical in correlating the evolution of the virus and migration of humans and also treatment responses of infected population. The symptom of the virus ranges from fever to jaundice and to a liver cirrhosis and hepatocellular carcinoma (HCC). Transmission of HBV is commonly via horizontal route in developing regions and in the developed regions; transmission occur more often among adults that use injectable drugs and high-risk sexual behaviors. Therefore, the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) have recommended HBV screening and vaccination to all travelers without an HBV immunization history before traveling to endemic regions. This chapter gives an overview on HBV as a potential traveler's infection.

**Keywords:** hepatitis B virus, travelers, vaccination, genotypes, travel medicine

## **1. Introduction**

Hepatitis B virus (HBV) is a partially double-stranded viral agent with a circular deoxyribose nucleic acid (DNA) that replicates by reverse transcription. HBV infection is a hepatocyte infection that is globally considered as a public health concern [1–3]. There are more than 2 billion persons infected with HBV living today worldwide with 260 million estimated to be chronically infected with the infection and having a carrier rate varying from 9 to 20% in Sub-Saharan Africa (SSA) [4–6]. Annually, there are close to 900,000 HBV-related deaths, mainly due to cirrhosis or hepatocellular carcinoma (HCC). The viral infection is the fourth most common vaccine preventable infection among travelers returning home ill after enteric fever, acute hepatitis A, and influenza [7, 8]. This viral agent can cause both acute and chronic infections. Many infected persons show no symptoms during the initial stage of the infection. Typically, the viral agent has an incubation period of 90 days (range, 60–150 days). The acute HBV infection that is acquired newly only shows symptoms rarely. Signs and symptoms of the viral infection differs with age; most children aged under 5 years old and newly infected immunosuppressed adults often show no symptoms, while about 30–50% of people that are more than 5 years of

age are usually symptomatic [7]. When present, the typical signs and symptoms of acute infection include malaise, fatigue, poor appetite, nausea, vomiting, abdominal pain, fever, dark urine, light color (clay-colored) stool, joint pain, and jaundice [8]. The overall case fatality ratio of acute infection due to HBV is approximately 1% [9]. People infected with HBV are susceptible to infection with hepatitis D virus; coinfection increases the risk of fulminant hepatitis and rapidly progressive liver disease [10]. Transmission of HBV is mainly through percutaneous or mucosal exposure to HBV-infected blood or bodily fluids including saliva or semen [2]. There are reports of transmission via sexual contact and contaminated medical equipment and through sharing of infected needles and injecting apparatus [11].

The prevalence of chronic HBV infection is ≥2%, such as in the western Pacific and African regions; expatriates, missionaries, and long-term development workers may be at increased risk for HBV infection in such countries [7, 8]. Serologic markers specific for the viral agent are necessary to diagnose HBV infection and for appropriate clinical management [12]. These markers can differentiate between acute, resolving, and chronic infections. Polymerase chain reaction (PCR) method can further be use to qualitatively or quantitatively detect the amount of HBV DNA in patients' specimen after checking the markers of the virus [13]. All travelers should be screened for HBV infection markers, so that they would not be at risk of acquiring the virus during their stay [7].
