On September 11, 2008, the index case, a mother of six children (family A), became ill. A week later, she was admitted to a hospital and diagnosed with hepatitis A. The state health department was notified by a laboratory on September 19 that the woman had a positive anti-HAV IgM result. She developed fulminant hepatitis and was transferred out of state to a tertiary care facility. Five of her six children living at home were subsequently diagnosed with hepatitis A, with onset dates ranging from September 11 to September 29 (). The sixth child at home was an infant adopted from Ethiopia in mid-August 2008 at 10 months of age. None of the family traveled overseas for the adoption; the child was brought to the U.S. by a staff member of an adoption agency. The staff member had been previously immunized against HAV and did not become ill. The child was asymptomatic. Upon testing on October 2, 2008, the infant was positive for IgM antibody to HAV. A stool sample from October 4 was positive for Giardia lamblia. The child reportedly had intermittent loose stools but no clearly defined diarrheal illness.
Characteristics of case patients in an outbreak of hepatitis A in Maine, 2008
Two members of the extended family became ill with hepatitis A on October 23. Both individuals had assisted in caring for the children of the index case after her hospitalization. Neither had received post-exposure prophylaxis, as they had not been identified during the initial contact investigation of family A by the state health department. One of the extended family members was an adult and required hospitalization. The other extended family member attended high school. No additional cases of hepatitis A were identified in the high school.
Two of the children in family A attended a local elementary school (school X) in kindergarten and third grade. On October 24, a fifth grader at the school was diagnosed with hepatitis A. No links between this child and family A outside of the school setting could be identified. Assuming the fifth grader was infected in the school setting, the state health department held a hepatitis A immunization clinic at the school on November 6. Hepatitis A immunization was offered at no charge to all students (n=208) and staff (n=51) at the school. Only three (1%) students reported a prior history of hepatitis A immunization. A total of 158 (76%) students and 50 (98%) staff were immunized during the clinic. By November 25, school nurses and private providers had immunized another 15 (7%) students. Four additional students at the school, of which only one was a classmate of a previous case, were subsequently diagnosed with hepatitis A from November 7 through November 25 ().
Cases in outbreak of hepatitis A by week of illness onset in Maine, 2008
In addition to immunization of students and staff at school X, control measures included improved hand hygiene and environmental initiatives. Hand hygiene was enhanced through educational efforts and installation of alcohol gel dispensers throughout the school. Environmental efforts included cleaning and disinfecting commonly used items such as computer keyboards and temporarily discontinuing the self-service salad bar in the school's cafeteria.
After the initial investigation, it was determined that one child of family A attended a local preschool. All children at the preschool were 3 to 5 years of age; none were in diapers. Only one of the students or staff at the preschool reported previous receipt of hepatitis A vaccine. An immunization clinic was held at the preschool on November 12. Nine (47%) of 19 children and one (33%) of three staff were immunized. No additional cases of hepatitis A were identified at the preschool or among family members.
None of the ill individuals in this outbreak had received hepatitis A vaccine more than a week prior to illness onset, except for a 6-year-old female with illness onset on November 25. She attended school X and was immunized on November 6. Her older brother had become ill with hepatitis A on November 10. All ill individuals made full recoveries.
On May 15, 2009, another hepatitis A immunization clinic was held at the school to deliver the second dose of the vaccine. Students and staff of the preschool were invited to attend. A total of 149 (72%) students and 52 (102%) staff of the elementary school were immunized at the clinic. Another four (2%) students and seven (14%) staff of the school were immunized by the school nurse during the following week. A second dose of vaccine was administered to four (21%) students from the preschool during the clinic.