Viral hepatitis update: Progress and perspectives

Table 1 Features of different types of hepatitis virus

	HAV	HBV	HCV	HDV	HEV
Family	Picornaviridae	Hepadnaviridae	Flaviviridae	Undefined1	Hepeviridae
Genus	Hepatovirus	Orthohepadnavirus	Hepacivirus	Deltavirus	Orthohepevirus
Genome	Positive single-stranded linear RNA	Double stranded gapped DNA	Positive single-stranded linear RNA	Negative single-stranded circular RNA	Positive single-stranded linear RNA
Genome length (kb)	7.5	3.2	9.6	1.7	7.2
Genotype	6 genotypes: I, II and III infect humans, and IV, V and VI infect non-human primates	10 genotypes (A to J)	8 (1 to 8)	8 (1 to 8)	8 (1 to 8)
Transmission	Fecal-oral	Parenteral, sexual, and perinatal	Exposure to infected blood	Exposure to infected blood and body fluids	Fecal-oral; zoonotic; blood transfusion
Treatment	None. In case of severe hepatitis, treatment of symptoms	Pegylated interferon-alpha and nucleoside/nucleotide analogues	DAA	Pegylated interferon-alpha	Ribavirin (in chronic HEV infection)
Prophylaxis	Yes (inactivated vaccine)	Yes (recombinant vaccine)	No	Yes (HBV vaccine)	No2
Clinical outcome of infection	Self-limited	Self-limited and chronic	Self-limited and chronic	Self-limited and chronic	Self-limited
Chronic infection rate	No	Depends on the age of acquisition of the infection. Birth or in infancy 90%, 1 yr and 5 yr of age 30%-50%, adulthood 5%. Hemodialysis patients 40%. Immune deficient patients 20%	80%	More frequent in HBV/HDV superinfection than coinfection	Acute infection in most of the cases. Chronic infection in immunosuppressed populations

¹It is not defined yet in any of the established viral families.

²There is only one vaccine, approved and used only in China. HAV: Hepatitis A virus; HBV: Hepatitis B virus; HCV: Hepatitis C virus; HDV: Hepatitis D virus; HEV: Hepatitis E virus; DAA: Direct antiviral agents.