With an estimated 257 million individuals worldwide living with hepatitis B virus (HBV), the disease constitutes a global health public issue, according to the World Health Organization.
 
Previously, little has been known about the origins and global spread of HBV-D and HBV-A, the most prevalent genotypes of the virus. A recent study published in eLife sought to establish the HBV dissemination patterns across different geographic regions for both genotypes. 
 
“The epidemiological history of HBV-D and HBV-A remains unclear due to a lack of relevant studies,” lead author Evangelia-Georgia Kostaki, PhD candidate in molecular epidemiology at the National and Kapodistrian University of Athens, said in a statement. “In order to uncover more of this detail, we wanted to establish how HBV was disseminated across different geographic regions.”
 
To accomplish this goal, the researchers used 916 HBV-D and 493 HBV-A full-genome sequences to reconstruct the genotypes’ evolutionary development and diversification, and analyze their levels of regional clustering.
 
Using this method, the researchers determined that the origin of HBV-D was in North Africa and the Middle East, although they were not able to locate the exact origin accurately. The researchers also found low levels of regional clustering for the Middle East and Southern Europe.
 
“We found low levels of HBV-D transmission occurred locally in North Africa and the Middle East, suggesting a high amount of movement among populations infected with HBV in these areas,” senior author Dimitrios Paraskevis, PhD, assistant professor of epidemiology and preventive medicine at the National and Kapodistrian University of Athens, said in the press release.
 
These findings are reflective of the history of human migration patterns in these areas, resulting in the spread of HBV-D, Dr Paraskevis noted.
 
For HBV-A, the analysis suggests the origin is close to Africa and Europe, and likely in the Middle East and Central Asia. Following HBV-A’s initial spread in Central Asia, the virus followed 2 distinct pathways: 1 to eastern and southern Africa and another to sub-Saharan and western Africa. The researchers indicated that the slave trade likely contributed to regional shifts in transmission towards Brazil, Haiti, and the Indian subcontinent
 
“We observed considerable differences in the global dissemination patterns of HBV-D and HBV-A and different levels of monophyletic clustering in relation of the regions of prevalence of each genotype,” the researchers concluded.   
 
References
 
Kostaki EG, Karamitros T, Stefanou G, et al. Unravelling the history of hepatitis B virus genotypes A and D infection using a full-genome phylogenetic and phylogeographic approach. eLife. 2018. Doi: 10.7554/eLife.36709
 
Scientists shed new light on hepatitis B virus origins [news release]. eLife’s website. https://elifesciences.org/for-the-press/2bc7c0e1/scientists-shed-new-light-on-hepatitis-b-virus-origins. Accessed August 8, 2018.