An Outbreak of Airborne Nosocomial Varicella Tracy L. Gustafson, MD, Gail B. Lavely, RN, Earl R. Brawner, Jr, BS, Robert H. Hutcheson, Jr, MD, peter F. Wright, MD, and William Schaffner, MD From the Field Services Division, Epidemiotogy program Office, Centers for Disease Control, Atlanta; Departments of Pediatrics and Medicine, Vanderbitt university Schoo/ of Medicine, Nashvitle, Iennessee,' and Divisions of Air Pollution Control and communicable Disease Control, rennessee Department of pubtic Heatth, Nashviile ABSTRACT. An outbreak of nosocomial varicella was traced to airborne spread from an immunocompromised child hospitalized from Nov 11-19, 1980. Seventy poten- tially susceptible children were hospitalized on the ward during that period. Although the index patient remained in strict room isolation throughout his hospital stay, eight of these patients contracted varicella. The afternoon of November 12 was the period of highest risk for acquiring varicella. Eight of 36 patients (22Vo) present that after- noon, compared to none of 34 patients not present that afternoon, acquired the infection. A patient's risk of con- tracting varicella was significantly related to how near he/she came to the index patient's room that afternoon. Airflow studies, using the tracer gas, sulfur hexafluoride (SFo), demonstrated that patient rooms on this ward were at positive pressure with respect to the corridor. Despite isolation procedures, SFu released in the index patient's room achieved concentrations in the corridor as high as LUVo of those inside the room. Airborne spread of varicella has rarely been reported, but it may be a common mode of transmission in hospitals. We suggest that patients hospitaltzed with varicella be placed in strict isolation in negative-pressure rooms to reduce the risk of nosocomial transmission. Pediatrics 70:550-bb6, Lg82; uaricella, air- borne transmission, nosocomial, outbreah, epidemiol- ogy. varicella, Iike measles, is a highly contagious childhood viral exanthem. Unlike measles, however, its modes of transmission are not clearly under- stood. Most textbooks suggest that children con- tract the disease by close contact with another child with the rash.t'2 Droplet spread or direct contact with vesicle fluid presumably permits the virus to enter the body through the mucous membranes of the upper respiratory tract.s The virus has been Received for publication Aug 91, 1981; accepted oct 21, 1gg1. Reprint requests to (T.L.G.) Epidemiology program office, Cen- ters for Disease Control, Atlanta, GA B0B3B. PEDIATRICS (ISSN 0091 400b). Copyright @ 1982 by the American Academy of Pediatrics. 55o PEDIATRICS vol. 70 No. 4 october 1982 isolated from the oropharynx of at least one patient shortly after household exposure.4 The fact that a child is infectious for one or two days prior to onset of the rash suggests that respiratory spread oc- curs.''' Nosocomial transmission of varicella is an in- creasingly serious problem, as immunocompro- mised children constitute a growing proportion of the hospitalized pediatric population. We report a nosocomial outbreak of varicella in which airborne transmission was strongly implicated. An airborne outbreak of varicella supported by airflow and epi- demiologic studies has been reported only once previously.5 We suggest that the airborne mode of transmission may be more common than the rare reports indicate. We emphasize that all hospitalized patients wiih varicella shculd be isolated ln nega- tive-pressure rooms to reduce the risk of airborne spread. OUTBREAK INVESTIGATION The index patient was an ll-year-oth boy with cartilage-hair hypoplasia, a disease associated with susceptibility to severe episodes of varicella.6,7 He developed a vesicular eruption on Nov G, 1980, two weeks after exposure to varicella at school. He was admitted to the hospital at 1 avr on November 11 because of progression of the rash. He was placed in strict isolation in a private room on the fifth floor (room 51), and did not leave that roorn during the ten days he was in the hospital. The patient had a generalized skin eruption that failed to crust normully, but he did not have a cough or roentgenographic evidence of pneumonia. He was treated for five days with intravenous adenine arabinoside (Ara-A) at a dose of 15 m;/k1/z4 hr. Therapy with adenine arabinoside began at 7:80 prvr on November 11. An attempt to culture varicella