**8. How HBV is diagnosed**

HBsAg is the standard diagnostic marker used to screen for HBV infection in travelers. A positive test depicts an acute or chronic infection [2]. Quantifying HBsAg (qHBsAg) is also an essential tool in staging of HBV infection and predicting responses to HBV treatment. This tool depend on both viral and host factors,

**307**

*Traveler's Infections: Overview of Hepatitis B Virus Infection*

such as genotype, preS/S gene variability, and hepatic disease stage [72]. The presence of hepatitis B envelope antigen (HBeAg) indicates that the virus is actively replicating and typically correlates with higher levels of HBV DNA. Immunoglobulin (Ig) G and IgM to hepatitis B core antigen indicates either that the individual has previously been infected or has an ongoing infection. IgG anti hepatitis B core (IgG anti-HBc) will often persists for life. The presence of anti-HBs shows that the individual has obtained immunity either from infection or vaccination [3, 6].

Touching upon the technical procedures behind the tests, tests for serological markers are carried out using different techniques, based on resources availability. Chemiluminescent microparticle immunoassay (CMIA) is one of those qualitative tests that detect the viral antigen in blood or serum. The technique has a high specificity and sensitivity and is based on the antigenic features (e.g., HBsAg or HBeAg) binding to commercially synthesized antibodies (anti-HB) with chemiluminescence [73]. The light produced in a chemiluminescent reaction can be measured. This method is more sensitive than the enzyme-linked immunosorbent

Polymerase chain reaction (PCR) is an advanced technique to detect HBV. It amplifies the nucleic acid and greatly enhances the amount of DNA [3]. This method can qualitatively or quantitatively detect the amount of HBV DNA in patients' specimen, which reflects the replicative condition of the virus. To monitor and manage HBV infection, then a quantitative detection method is the technique of choice [73]. ALT levels are measured to help determine liver inflammation. ALT is an enzyme that is normally found in the liver, but also present in other body tissue, that is discharged into the circulation system as a consequence to hepatocellular injury [26]. ALT plays a role in characterization of HBV infection phases in synergy with HBV DNA [74]. Different noninvasive diagnoses such as aspartate aminotransferase (AST), platelet ratio index (APRI), and transient elastography (FibroScan) still exist. APRI is an index to determine the hepatic fibrosis based on a formula derived from platelet and AST concentrations [3]. FibroScan measures grade of liver fibroses through the detection of liver stiffness. Both methods are recommended by WHO to evaluate cirrhosis presence, but while FibroScan is preferred in a context where availability and cost is not an issue, APRI is used in settings with limited resources. Liver biopsy has been used to assess degree of necroinflammation and fibrosis degrees. However, the method has

All travelers should be screened for HBV infection markers, so that they will not be at risk of acquiring the virus during stay [74]. Recently updated guidelines also recommend that pregnant women with chronic HBV be referred to a specialist and considered for HBV treatment to further reduce the chance of transmitting the virus [3]. In infants born to HBsAg-positive mothers, the risk of mother-to-child transmission is significantly greater if the mother is positive for HBeAg, has a high viral load, and/or is infected with HIV [33]. Such infants should be given both vaccine and HBIgG (0.5 ml) within 12 hours of delivery. The infants should be evaluated for HBsAg, anti-HBs, and anti-HBc at age 12 months. The presence of anti-HBs depicts vaccine-induced immunity, and detection of both anti-HBs and anti-HBc shows immunoprophylaxis-modified infection, whereas the presence of HBsAg

Individuals who have not received the HBV vaccination and are exposed to the virus (through needle stick injury, splashing, or sexual exposure to partners

*DOI: http://dx.doi.org/10.5772/intechopen.92174*

diverse demerits and constraints [6, 75].

indicates prophylaxis failure [15, 76, 77].

**9. How HBV infection is prevented and controlled**

assay (ELISA) [73].

#### *Traveler's Infections: Overview of Hepatitis B Virus Infection DOI: http://dx.doi.org/10.5772/intechopen.92174*

*Tourism*

5%, doubling that of the general population in a Swedish expatriate's population. Short duration of travel stay will obviously lower the risk of the infection [53]. Nielsen et al. reported that the incidence per month of HBV infection was 10.2 per 100,000 with 62% of cases traveling for less than 4 weeks [54]. Most research is hinged on travelers becoming sick after travel before testing to occur, so this tends

Many cross-sectional research have find out that travelers have reduced baseline understanding on infections related to travels and put themselves in jeopardy to HBV infection through their actions while in foreign land [47, 55]. Nielsen et al. reported that 5% of short-term and 5% nonimmune travelers were under a great risk of getting infected with HBV via tattooing, injections, and operation activities [44]. About 41% high-risk endeavors were reported among travelers in more than 6 months with most of the endeavors being unintentional and involuntary [44]. In a retrospective study among Australian travelers, 281 (56%) had visited a country with medium to high prevalence of HBV, of whom only 43% had been vaccinated and 162 (33%) undertook activities associated with potential HBV exposure [55]. Medical tourism and transplantation of organs have been identified several times as predictors for the viral agent, which highlights that checking for transmissible infection cannot be guaranteed universally [56, 57]. A study among Australian patients finds out that 2 of 16 who traveled overseas for commercial kidney transplantation developed fulminant hepatitis related to HBV infection and died [58]. Significantly high-incidence rate of HBV infection was reported among patients

to underestimate the incidence of the viral infection [7, 49].

receiving renal transplantations in India than in Saudi Arabia [59].

Hepatitis B virus until now has been reported to have 10 genotypes (A–J) with

One of the three genotypes A, D, and E is predominantly circulating in Africa

regions, and genotype D is predominantly circulating in the Northern Africa region. Genotype E is more in most of SSA regions including Nigeria; this report excludes Uganda and Cameroon which are predominant with the A genotype [5, 60, 64, 65]. Genotype A is prevalent in Europe and Southeast Asia, including the Philippines [43, 66]. Genotypes B and C are predominant in Asia [67]; genotype D is common in the Mediterranean area, the Middle East, and India; genotype F is common in Central and South America [66]. Genotype G has been identified in Germany and France [67]. Genotype I has been detected in Laos, Vietnam, and China [68, 69], while the newest genotype J was identified in the Ryukyu Island in Japan [70, 71].

HBsAg is the standard diagnostic marker used to screen for HBV infection in travelers. A positive test depicts an acute or chronic infection [2]. Quantifying HBsAg (qHBsAg) is also an essential tool in staging of HBV infection and predicting responses to HBV treatment. This tool depend on both viral and host factors,

identified peculiar distribution based on regions to its high degree of genetic heterogeneity [5, 60–62]. HBV genotyping is significant in diverse ways. First, it provides global data on the genotypic distribution of the virus including phylogenetic and phylogeographic evidence. Second, it justifies the relationship between the viral strain and course of disease. It makes us understand the role of human

depending on the country. Genotype A is found in the Southern and Eastern

**7. Genotypic distribution of HBV**

**8. How HBV is diagnosed**

migration on the evolution of the virus [63, 64].

**306**

such as genotype, preS/S gene variability, and hepatic disease stage [72]. The presence of hepatitis B envelope antigen (HBeAg) indicates that the virus is actively replicating and typically correlates with higher levels of HBV DNA. Immunoglobulin (Ig) G and IgM to hepatitis B core antigen indicates either that the individual has previously been infected or has an ongoing infection. IgG anti hepatitis B core (IgG anti-HBc) will often persists for life. The presence of anti-HBs shows that the individual has obtained immunity either from infection or vaccination [3, 6].

Touching upon the technical procedures behind the tests, tests for serological markers are carried out using different techniques, based on resources availability. Chemiluminescent microparticle immunoassay (CMIA) is one of those qualitative tests that detect the viral antigen in blood or serum. The technique has a high specificity and sensitivity and is based on the antigenic features (e.g., HBsAg or HBeAg) binding to commercially synthesized antibodies (anti-HB) with chemiluminescence [73]. The light produced in a chemiluminescent reaction can be measured. This method is more sensitive than the enzyme-linked immunosorbent assay (ELISA) [73].

Polymerase chain reaction (PCR) is an advanced technique to detect HBV. It amplifies the nucleic acid and greatly enhances the amount of DNA [3]. This method can qualitatively or quantitatively detect the amount of HBV DNA in patients' specimen, which reflects the replicative condition of the virus. To monitor and manage HBV infection, then a quantitative detection method is the technique of choice [73]. ALT levels are measured to help determine liver inflammation. ALT is an enzyme that is normally found in the liver, but also present in other body tissue, that is discharged into the circulation system as a consequence to hepatocellular injury [26]. ALT plays a role in characterization of HBV infection phases in synergy with HBV DNA [74]. Different noninvasive diagnoses such as aspartate aminotransferase (AST), platelet ratio index (APRI), and transient elastography (FibroScan) still exist. APRI is an index to determine the hepatic fibrosis based on a formula derived from platelet and AST concentrations [3]. FibroScan measures grade of liver fibroses through the detection of liver stiffness. Both methods are recommended by WHO to evaluate cirrhosis presence, but while FibroScan is preferred in a context where availability and cost is not an issue, APRI is used in settings with limited resources. Liver biopsy has been used to assess degree of necroinflammation and fibrosis degrees. However, the method has diverse demerits and constraints [6, 75].
