Table 2.
Epidemiology and clinical features of HEV infection in developing and developed countries.
| Item | HEV in developing countries | HEV in developed countries |
|---|---|---|
| Epidemiology | ||
| Genotypes | 1 and 2 | 3 and 4 |
| Source of infection | Human | Zoonotic; pigs are primary hosta |
| Route of infection | Fecal-oral via infected water | Fecal-oral via infected pig meat, direct exposure, infected water |
| Transfusion-related infection | Yes | Yes |
| Seroprevalence | Low in children up to 15 years old, increases rapidly from ages 15 to 30 | Steady increase throughout age groups |
| Incidence | Variable: 64/1,000 patient/year, Bangladesh | Variable: 3/100 patients/year, South of France; 7/1,000 patients/year, USA |
| Yes; can involve thousands of cases | No; occasional small case clusters from a food point source | |
| Attack rate | 1 in 2 | 67–89% of those infected are asymptomatic |
| Person-to-person spread | Very limited | No |
| Seasonality | Yes; outbreaks occur at times of flooding/monsoon | No |
| Disease in travelers returning from areas of endemicity | Well-described | Is beginning to emerge as high-risk areas become defined |
| Clinical features | ||
| Age of infection (yr) | 15–30 | >50 |
| Sex (male/female ratio) | 2:1 | >3:1 |
| Clinical course | Self-limiting hepatitis | Self-limiting hepatitis |
| Neurological complications | Yes | Yes |
| Deaths in pregnant females | Yes; 20–25% in final trimesterb | No |
| Outcome in patients with underlying chronic liver disease | Poor | Poor |
| Chronic infection | No | Yes; genotype 3 only unknown |
| Burden of disease | 3.4 million cases/yr, 70,000 deaths, 3,000 stillbirths | Unknown |
a
HEV genotypes 3 and 4 have also been transmitted from human to human via infected blood products.
b
The epidemiology and clinical course of HEV genotype 1 in Egypt are significantly different from those in other developing countries. In Egypt, the seroprevalence is similar to that of HAV, with nearly universal exposure in childhood, and the risks to pregnant females may be less. The reason for these observations is unknown.
cData are for 9 of 21 regions defined for the Global Burden of Diseases, Injuries and Risk Factors Study (37), which represent 71% of the world's population.