R. Gordon Douglas

Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential.

To examine intrafamily spread of respiratory syncytial virus infections and their associated illnesses, 36 families with 188 members were studied during an outbreak of such infections. Nurses visited every three to four days to obtain specimens for viral isolation and interview household members. The virus infected 44.4 per cent of families, and 21.9 per cent of all members. All age groups had appreciable attack rates (with a range of 16.8 per cent in adults to 29.4 per cent in infants). In infected families, 45.9 per cent of members became infected, including 10 of 16 infants. Secondary attack rate for all ages was 27 per cent, and that for infants 45.4 per cent. An infant's older sibling appeared most likely to introduce the virus into the family. Associated acute respiratory illnesses occurred in 94.9 per cent of cases, and appeared more severe than those not associated with respiratory syncytial virus. When the virus was introduced into a family the high attack rate produced an illness of age-related severity.

We studied the frequency and severity of respiratory syncytial virus infections acquired nosocomially on an infants' ward during a community outbreak. Every three or four days all infants and staff were examined, and specimens were obtained for viral isolation. During two months, 14 of 44 contact infants acquired the virus. All were ill, and four had pneumonia. Infected infants had a significantly longer mean hospital stay (21.5 days) than uninfected ones (9.2 days, P less than 0.001). Risk of nosocomial infection could not be related to age or to underlying disease, but was linked to length of hospitalization: 45 per cent of infants hospitalized for one week or more became infected, and the percentage increased with length of stay. Ten of 24 staff members also acquired the virus and appeared to play a major role as virus carriers. Nosocomial respiratory syncytial virus infection poses a major risk for hospitalized infants and adds to hospital costs.

Respiratory syncytial virus infections are thought to be uncommon in the first month of life. During a community outbreak, we prospectively studied such infection in our neonatal units. Of 82 neonates studied, 66 were hospitalized for six days or longer, and 23 (35 per cent) acquired this virus. Four infants died, two unexpectedly. Infected infants had a significantly shorter gestation and birth weight. Illness was often atypical, with nonspecific signs, especially in infants under three weeks of age, who had significantly less lower-respiratory-tract involvement and lower quantities of virus in their nasal washes. The titer of virus shed correlated with the infants' postnatal, but not gestational, age. Infection was also acquired by 34 per cent of the staff, who appeared to be important in the spread of the virus. These findings suggest that respiratory syncytial virus may readily infect neonates, but the disease may be atypical and may be overlooked.