The evolving epidemiology of hepatitis a in the United States: incidence and molecular epidemiology from population-based surveillance, 2005-2007.
BACKGROUND
The incidence of hepatitis A virus (HAV) disease is the lowest ever in the United States. We describe recent incidence and characteristics of cases of HAV disease from 6 US sites conducting hepatitis surveillance in the Emerging Infections Program.


METHODS
Health departments conducted enhanced, population-based surveillance for HAV from 2005 through 2007. Demographic and risk factor data were collected on suspected cases (persons with a positive IgM anti-HAV result) using a standard form. Remnant serum specimens from a convenience sample of cases were tested by polymerase chain reaction, followed by sequencing the 315-nucleotide segment of the VP1-P2B junction.


RESULTS
There were 1156 HAV cases reported during 2005 through 2007. The combined population under surveillance was 29.8 million in 2007. The overall annual incidence rate was 1.3 per 100 000 population (range by site, 0.7-2.3). Of reported cases, 53.4% were male, 42.4% were white, 44.7% were aged 15 to 39 years, and 91.4% resided in urban areas. Reported risk factors were international travel (45.8%), contact with a case (14.8%), employee or child in a daycare center (7.6%), exposure during a food or waterborne common-source outbreak (7.2%), illicit drug use (4.3%), and men who had sex with men (3.9%). Genotypes among the 271 case specimens were IA (87.8%), IB (11.4%), and IIIA (0.7%). Of the 271 polymerase chain reaction-positive specimens, 131 (48.3%) were from cases reporting travel or exposure to a traveler; 58 of the 131 cases reported travel to Mexico, and 53 of the 58 were within the US-IA(1) cluster.


CONCLUSIONS
International travel was the predominant risk factor for HAV transmission. Health care providers should encourage vaccination of at-risk travelers.
Division of Viral Hepatitis, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, 1600 Clifton Rd, MS G-37, Atlanta, Georgia 30333, USA. rmk2@cdc.gov
R Monina
RM
Klevens
Jeremy T
JT
Miller
Kashif
K
Iqbal
Ann
A
Thomas
Elena M
EM
Rizzo
Heather
H
Hanson
Kristin
K
Sweet
Quyen
Q
Phan
Alicia
A
Cronquist
Yury
Y
Khudyakov
Guo-liang
GL
Xia
Philip
P
Spradling
D000293:Adolescent; D000328:Adult; D004279:DNA, Viral / Q000032:analysis*; D004196:Disease Outbreaks; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology* / Q000821:virology; D030041:Hepatitis A virus / Q000235:genetics*; D006801:Humans; D015994:Incidence; D008297:Male; D017720:Molecular Epidemiology; D016133:Polymerase Chain Reaction; D011159:Population Surveillance / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult
D004279:DNA, Viral