Clinical Features and Transmission Pattern of Hepatitis A: An Experience from a Hepatitis A Outbreak Caused by Two Cocirculating Genotypes in Sri Lanka

Abstract

Sri Lanka is one of the intermediate-endemic areas for hepatitis A virus (HAV), and concerns exist about the increasing HAV-susceptible population. In fact, Sri Lanka recorded a large hepatitis outbreak, possibly hepatitis A, around the end of the Sri Lankan war. It included more than 14,000 patients consisting of local residents, internally displaced personnel, and military personnel in the main combat zone. The outbreak had slowed down by October 2009; however, acute viral hepatitis continued to occur sequentially among military personnel. We obtained clinical information and serum samples from 222 patients with acute hepatitis who visited the Military Hospital Anuradhapura between January and September 2010. Samples were subjected to laboratory testing including HAV-immunoglobulin M and genotyping. Most patients (98.2%) were confirmed as having hepatitis A belonging to two subgenotypes: IA and IIIA. We did not observe any differences in clinical or biochemical features among patients with subgenotypes IA and IIIA except for pale stools and upper abdominal discomfort. During the investigation period, we observed a serial outbreak caused by identical HAV strains with an interval in line with that of typical HAV incubation periods. Most patients in the first outbreak were found in the training center, and patients in the second outbreak were found in multiple places where soldiers were assigned after the training center. These findings indicate that a strain of HAV diffused from one place to another along with movement of infected persons among the HAV-susceptible population. HAV vaccination for high-risk groups, such as young soldiers, is necessary.

Figure 1.

The trend of number of hepatitis A patients who visited to the Military Hospital Anuradhapura during investigation period.

Figure 2.

Geographic distribution of investigation areas. Numbers = area code number; MHA = Military Hospital Anuradhapura; Tr = training center.

Figure 3.

Neighbor-joining phylogenetic tree of the nucleotide sequences of the VP1/2A junction region from the representative hepatitis A virus strains in this study. Reference sequences, subgenotype IA; GBM/WT (accession no. X75215) and subgenotype IIIA; PN_IND/India (accession no. EU011791) were retrieved from GenBank database. The scale bar indicates nucleotide distance.

Figure 4.

The first and second outbreaks caused by cluster IA1. During February 20–March 1, 8 patients with IA1 genotype visited the Military Hospital Anuradhapura (MHA). Of them, six patients were possibly infected in training center-1 (Tr1). One month later, from March 22 to April 10, 20 patients visited the MHA. Their representative infection areas were distributed into nine areas. Numbers in the explanatory note show area code.