Pediatric emergency medicine trisk 2090 2090
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the 2-week period before onset of jaundice or elevation of liver enzymes,
when concentration of virus in stool is highest. Highly effective vaccines exist
for its prevention for travelers over 12 months of age. The vaccine is sufficient
for most patients; however, an immunoglobulin is an option for high-risk
individuals, such as patients under 12 months of age or patients with an
underlying liver disease traveling to an endemic area. On a worldwide scale,
fewer than 5% of cases are recognized clinically. HAV is a rare cause of
fulminant hepatitis. No chronic carrier state exists. The virus is maintained in
the human population through person-to-person transmission, and there is no
evidence of maternal to neonate transmission. About 30% of the population of
the United States shows evidence of past infection. Immunization of children
(1 to 18 years of age) consists of two or three doses of the vaccine. Adults
need a booster dose 6 to 12 months following the initial dose of vaccine. The
vaccine is thought to be effective for 15 to 20 years or more. Because
Hepatitis A vaccine is inactivated, no special precautions need to be taken
when vaccinating immunocompromised persons.
HBV is endemic in the human population. Although predominantly
transmitted by the parenteral route or sexual contact, the high incidence of
infection in family contacts suggests that the virus may also spread by saliva
or breast milk. The ability of HBV to produce a chronic carrier state in the
DNA in 5% to 10% of infected subjects allows maintenance of an infectious
pool without serial transmission. Children who contract HBV at birth have a
25% chance of dying from a liver-related cause. HBV vaccine provides
protection against hepatitis B for 15 years and possibly much longer.
Currently, the Center for Disease Control and Prevention recommends that all
newborns and individuals up to 18 years of age be vaccinated. Three
injections over a 6- to 12-month period are required to provide full protection.
HCV accounts for about 95% of hepatitis infections in recipients of blood
transfusion and 50% of cases of sporadic non-A, non-B hepatitis. Most of
these patients will progress to chronic hepatitis, and about 20% will develop
cirrhosis. Perinatal transmission of HCV is the most common source in
children. Maternally acquired antibodies can persist in an infant, so patients
should not be tested for perinatally acquired disease until after the infant is 18
months of age.
HDV requires hepatitis B helper functions for its propagation in
hepatocytes. The disease may occur either simultaneously with hepatitis B
infection (coinfection) or as superinfection in chronic hepatitis B carriers.
