Viral hepatitis is caused by at least five distinct viruses, referred to as hepatitis A, B, C, D, and E viruses. Hepatitis types A and E are enterically transmitted viruses, while types B, C, and D are predominantly transmitted through percutaneous exposures to blood and by sexual contact. Transmission of hepatitis A virus (HAV) occurs readily between children in day care and adult contacts; hepatitis A outbreaks are the most prevalent type of hepatitis observed in the day-care setting. Transmission of hepatitis B virus (HBV) between children in day-care centers has occurred only in isolated circumstances. Hepatitis C and hepatitis D occur primarily among adults, and transmission has not been documented in day-care settings, while hepatitis E occurs only among travelers to less developed countries where this infection is common.
This article discusses the epidemiology, prevention, and control of HAV and HBV in day-care centers.
HEPATITIS A IN DAY-CARE SETTINGS
Hepatitis A virus replicates in the liver and is shed in the stool of infected persons. The major mode of HAV transmission is therefore fecal-oral, with disease spread occurring most commonly by person-to-person transmission.1 Because young children often have inadequate hygienic practices or lack toilet training, and because children in day-care centers have close interaction, these settings are a common site for hepatitis A outbreaks.
The incubation period for HAV infection averages 28 days (range: 15 to 50 days), and clinical illness is self-limited and usually does not persist more than 2 months. Symptoms and signs of infection may include jaundice, dark urine, diarrhea, fever, malaise, anorexia, nausea and vomiting, myalgia, and abdominal pain. However, children are much less likely than adults to have overt symptoms when infected. Approximately 50% of infected children under the age of 6 are asymptomatic, and many of the remainder have mild symptoms without jaundice. Children older than 6 and adults usually (more than 75%) develop specific symptoms with jaundice and dark urine.
Diagnosis of HAV infection depends on the demonstration of IgM antibodies to HAV (IgM antiHAV) in serum, usually detectable by commercial assays within a week of onset of illness and persisting for 2 to 6 months thereafter. Presence of total IgG anti-HAV with negative IgM anti-HAV signifies prior HAV infection and permanent immunity.
Outbreaks of hepatitis A have been recognized in day-care centers since the early 197Os.2'3 Hepatitis A cases acquired in day-care centers form an important contribution to total hepatitis A cases in the United States and are occasionally the source of larger community-wide outbreaks. Between 13% and 15% of hepatitis A cases reported nationwide occur among day-care center children or employees, or their close contacts.4
Extensive studies of outbreaks have characterized features of hepatitis A in day-care settings.2'3'5 Outbreaks ranging from 3 to 50 cases occur most frequently in large centers that enroll children Jn diapers. Hepatitis A infection is more likely to be introduced at centers that have greater numbers of children, that are open for a greater number of hours, and that enroll children younger than 2 years of age. Once infection is introduced, the rate of spread of infection is most closely related to the number of children of diaper-wearing age and the inadequacy of diaper-changing facilities and practices such as diaper changing by food preparers) at the center. In centers where children of different ages attend (including children with and without diapers), infection is usually not confined to specific classrooms but spreads throughout the whole center because children of different ages mingle before and after scheduled hours and because of household spread among siblings. Wide dissemination of infection is unlikely in centers with only older, toilet-trained children.
Because HAV infection in children under the age of 6 is usually mild and nonspecific or asymptomatic, outbreaks are usually recognized when adult contacts become ill. In outbreaks associated with day-care centers, parents of children are most often (70% to 80%) the persons who become clinically ill, followed by center employees (15%). Nonhousehold contacts of attendees (extended family members or babysitters) also may become ill. The handling of soiled diapers is the most important risk factor for infection among adults; adult contacts most likely to become ill are those with contact to children in diapers. Thus, parents and staff caring for toddlers are several-fold more likely to become ill than those exposed only to older children. Therefore, hepatitis A in an adult who has a child in day care should raise the index of suspicion that the child may be the source of infection and that an outbreak is occurring at the center. If the child contact is positive for IgM anti-HAV, then further investigation and control measures at the center are indicated.
Prevention and Control
Preventive measures for hepatitis A in day-care centers are those recommended to prevent the spread of enteric diseases in general (Table 1 ). The most important measure is good hygiene, including handwashing by staff after changing diapers and by children and staff before handling or eating food and after bathroom activities. Education and training of staff regarding good hygienic practices and modes of transmission of hepatitis A and other enteric diseases are essential. Adequate facilities must be available for diaper changing. Because HAV can survive for extended periods of time (at least 2 weeks) on environmental surfaces and fomite contamination may contribute to disease spread, periodic disinfection of environmental surfaces, shared toys, and other classroom objects with a diluted solution of sodium hypochlorite (household bleach, 1A cup to 1 gallon of water) is recommended, especially in infant and toddler areas
Early recognition of hepatitis A cases associated with day-care centers is important to help control potential outbreaks. Any child at a day-care center with jaundice or diarrhea should be excluded from attendance and be evaluated for the cause of the symptom(s), including testing for IgM anti-HAV. An outbreak of hepatitis A at a day-care center usually will be recognized because of disease in one or more household contacts of a center child. If a household contact of a child attending a day-care center is diagnosed with hepatitis A, then that child should be tested for IgM anti-HAV to determine whether the child might be asymptomatically infected. Cases in adults in several families with children at the same center should be considered day-care related unless proven otherwise.
Hepatitis A in Day-Care Centers
If a child who attends day care or if an employee is diagnosed with hepatitis A, administration of immune globulin to other center attendees and employees is recommended (Table I).6'7 Immune globulin administration is also recommended if cases occur in two families with children in the same center. Because disease at centers where there are children in diapers is rarely confined to a single age group or classroom, immune globulin should be given to all children and employees at such centers, regardless of age or classroom. In centers where only older, toilet-trained children attend, the risk of transmission is less, and immune globulin administration can be limited to classroom contacts (children and employees) of the infected child.
In addition to immune globulin administration at the center, efforts should be made to prevent spread to families of center attendees and to the community. This should include an information letter to parents explaining that their children should not be removed from the affected center and enrolled in other centers, because this might spread disease to other centers. Day-care centers should not be closed during outbreaks for the same reason. Administration of immune globulin to household contacts of diapered children attending a day-care center is recommended in hepatitis outbreaks in which three or more families are affected or in which recognition of the outbreak occurs more than 3 weeks after onset of the first case.7
Aggressive use of immune globulin among children and personnel at day-care centers with recognized hepatitis A cases is effective in reducing HAV transmission within centers and from centers to the general community. Nevertheless, protection afforded by immune globulin is temporary, and day-care outbreaks continue to occur. In recent years, several hepatitis A vaccines, including both killed and attenuated virus vaccines, have been developed.8 Initial studies have shown the vaccines to be highly immunogenic and to have minimal side effects, and studies are ongoing to evaluate the efficacy of these vaccines. If these vaccines prove to be efficacious, they will become important methods for preventing and controlling hepatitis A in the day-care setting. Vaccination could eventually be recommended for children and staff at day-care centers with diapered children.
HEPATITIS B IN DAY-CARE SETTINGS
Hepatitis B virus is found in high concentrations in the blood and blood-derived body fluids (eg, exudates from impetigo) of infected persons; saliva and other body fluids have much lower (1/1CXX)) HBV concentrations and are proportionately less effective in viral transmission. The virus is transmitted most commonly by percutaneous blood exposure (eg, transfusions or needlesticks), during sexual intercourse, and perinatally from mother to infants at the time of birth.9 Person-to-person transmission of HBV can occur in situations of close personal contact for extended periods, such as between family members in households and in institutions for the developmentally disabled. Transmission in these settings likely occurs by percutaneous exposure through bites, scratches, open skin lesions, sharing razor blades or toothbrushes, and possibly other fomites, although specific routes of transmission are rarely identified.
The incubation period of HBV ranges from 6 weeks to 6 months. Acute HBV infection produces symptoms of viral hepatitis in 5% to 15% of children of day-care age, yet is symptomatic in 33% to 50% of adults.10 Infection usually resolves with the development of protective antibodies, but may develop into a chronic infection (the carrier state). Children under the age of 5 have a 20% to 50% risk of becoming carriers of the virus after acute infection, while for older children and adults the risk is 5% to 10%. Children who develop chronic HBV infection may have a 25% risk of dying from cirrhosis or liver cancer.11
Diagnosis of HBV infection is confirmed by serologie testing for viral antigens and associated antibodies. The presence of hepatitis B surface antigen (HBsAg) indicates acute or chronic infection and potential infectivity to others; the presence of hepatitis B e antigen (HBeAg) correlates with greater infectivity. IgM antibody to the hepatitis B core antigen (IgM anti- HBc) is detectable for up to 6 months after the onset of illness; its presence indicates acute infection. Persons are defined as carriers if HBsAg remains positive for longer than 6 months. In persons who recover from infection, HBsAg disappears and antibody to HBsAg (anti-HBs) develops and is responsible for long-term immunity.
Because person-to-person transmission can occur in households and other settings, concern has been raised about the risk of transmission from children infected with HBV to other children or staff in day-care settings. A limited number of studies have investigated HBV exposures in day-care centers. In Washington, DC, a 4-year-old carrier child transmitted HBV to one of 24 other children at a day-care center during a 3-month period; the carrier child had a history of aggressive behavior, including biting and scratching.12 In Rome, Italy, an 18-month-old boy developed acute hepatitis B, and investigation of family and day-care contacts revealed only a 2 -yearold HBV carrier girl who attended the same day-care center as a possible source.13 A serosurvey of attendees at several nursery schools in Okinawa, Japan, where hepatitis B is endemic, identified several HBsAg positive children who did not have infectious members in their immediate families, suggesting possible transmission from HBV carriers within the nursery school; however, other possible sources of infection in the extended families or neighborhood were not ruled out.14
Hepatitis B in Day-Care Centers
Two other prospective studies have not demonstrated HBV transmission in day care despite longterm contact. These studies involved children who were discovered to be HBV carriers after attending day-care centers for more than a year; one of the children had severe eczema that frequently bled and required dressing by center staff. In both of these situations, no transmission was observed to other children or staff.12'15
Because the recognized instances of transmission are few and the opportunities for child-to-child transfer of blood or body fluids are rare, the risk of HBV transmission from children who do not have aggressive behavior or medical conditions that might facilitate transmission appears to be low. Nevertheless, because of the limited number of studies, the risk of HBV transmission in day-care settings cannot be precisely quantified, and further research is needed.
Prevention and Control
Hepatitis B virus transmission between children in day care is mostly likely to occur by direct transfer of blood or body fluids by bites and by scratches that break the skin. Precautions for the prevention of hepatitis B in day-care centers are therefore directed toward preventing transfer of blood or body fluids from one person to another (Table 2). These precautions include educating personnel about transmission and prevention of bloodbome diseases and covering any open skin lesions. The risk of environmental transmission of HBV and indirect transmission by objects contaminated with saliva is low; however, environmental surfaces should be cleaned, and toys and other objects that might be mouthed or shared should be disinfected periodically (Table 2).
If a child is known to be an HBV carrier, then a decision must be made regarding admission to a center and whether any restrictions should be considered if the child is to attend day care. Because of the apparently low risk of HBV transmission in day-care settings, routine exclusion of carrier children or screening of children as a criterion for entering day care is not justified. Instead, known HBV carrier children who do not exhibit aggressive behavior or have medical conditions such as dermatitis should be permitted to attend day care, and general precautions to prevent transmission of bloodbome diseases should be followed. In the event of a bite, needlestick, or other percutaneous exposure, postexposure prophylaxis with hepatitis B immune globulin and hepatitis B vaccine is indicated. The center director and primary caretaker should be aware that the child is an HBV carrier so that precautions can be taken if such specific exposures occur and to monitor behavior. For a known HBV carrier child who exhibits aggressive behavior, a decision regarding day care attendance should be made with consultation among the day-care center director, medical consultant, and local public health officials. Because these children may pose a risk to others, either exclusion from day care or hepatitis B vaccination (see below) of all day-care contacts are the best alternatives. If a decision is made to exclude, the child should be evaluated periodically to determine if his or her behavior has changed over time.
To detect possible transmission in day-care centers, it is important for hepatitis B cases occurring in young children to be reported to local health authorities and for all possible sources of infection, including day care, to be carefully assessed.
Immunization with hepatitis B vaccine is highly effective in preventing HBV infection and its consequences. More than 95% of children who receive the vaccine respond, and the duration of protection is at least 10 years. Because the current vaccination strategy of targeting individuals with high-risk behaviors has not had a major impact on hepatitis B rates in the United States,16'17 the Immunization Practices Advisory Committee and the American Academy of Pediatrics have recently endorsed a strategy of universal infant immunization, integrating the hepatitis B vaccine into the routine infant immunization schedule. Final approval of this recommendation is expected later this year. With implementation of this strategy, eventually all children of day-care age will be vaccinated, thereby eliminating the risk of HBV transmission.
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Hepatitis A in Day-Care Centers
Hepatitis B in Day-Care Centers