Spread of Varicella-Zoster Virus DNA to Family Members and Environments From Siblings With Varicella in a Household

Abstract

Objective. To elucidate virus spread from siblings with varicella to other family members and environmental objects in a family setting before and after onset of the disease. Materials and Methods. Among a family consisting of five members, a boy developed varicella and the remaining two siblings developed the disease 17 and 18 days after onset of the index case. Swab samples from throats and hands of parents and three siblings and samples from several sources in the environment of the house were collected frequently before and/or after onset of the disease. Varicella-zoster virus (VZV) DNA in the samples was examined by a sensitive polymerase chain reaction amplification assay. Results. In total, 108 samples from the throats and hands of the three children with varicella, 72 such samples from parents, and 72 samples from the surfaces of several sources in the house were collected. Eight days after onset of the index case (the older boy), VZV DNA was detected in both samples from the index case and on the surfaces of four sources (air conditioner filter, table, television channel push-buttons, and door handle), but not from the two other siblings or parents. Then, it was detected once on the mother's hand and the air conditioner filter and three times on the television channel push-buttons by January 30, 1998, when the girl developed varicella, 17 days after onset of the index case. The younger brother developed the disease on January 31. Viral DNA could not be detected in any samples obtained on January 30; however, it was detected on the hands of the older boy and the father and in samples from the hand and throat of the girl on January 31. Thereafter, virus DNA was detected three times intermittently by February 13 on the hand and three times persistently in the throat of the girl. The virus DNA was detected three times between February 1 and 3 on the hand and three times between February 1 and 4 in the throat of the younger boy. It was detected occasionally on the hands of the older boy and the parents, and occasionally or intermittently on surfaces of four environmental sources between February 2 and 13. Conclusions. The present study showed the rapid and broad contamination of the environment with the VZV DNA when the varicella patient appeared in a family, although it does not directly mean infectivity.