Child care may affect entire community's risks of infection

Any parent knows how quickly a cold or a cough can spread between children who play together. However, child care may also affect an entire community's carriage of potentially dangerous bacteria known as Streptococcus pneumoniae, according to an article in the April 1 issue of Clinical Infectious Diseases, now available online.

S. pneumoniae often exists in the nose and throat without causing problems, but if the bacteria grow out of control, they may result in illness ranging from minor conditions such as ear infections to more serious diseases like sinusitis, pneumonia, and meningitis.

A childhood vaccine released in 2000 has decreased rates of illness due to S. pneumoniae, also known as pneumococcus. Children are more likely to carry pneumococci than adults, and in a large group child care center, kids can easily spread the bacteria to their playmates through close contact.

The level of pneumococcal carriage varies widely between communities, and Harvard Medical School researchers hypothesized that one influence might be the extent of child care use. Using data from 742 children in 16 Massachusetts communities, they created a theoretical mathematical model that indicates that child care seems to affect pneumococcal carriage in individuals as well as in communities.

Individually, the model predicts the risk of pneumococcal carriage is two to three times higher for a child who attends child care than for a non-attendee. The model goes one step further: it predicts that communities with more children in child care for a longer period of time have higher carriage rates of pneumococcus among both child care attendees and non-attendees. The study suggests that child care attendance may account for large variations in total community pneumococcal carriage.

The researchers don't dissuade parents from using child care, despite the large group centers' apparent role in increasing the risk of infection. "I think that child care or any group play situation has real developmental and social benefits," said lead author Susan Huang, MD, MPH, of Harvard Medical School and Brigham and Women's Hospital. "The take-home message really relates to key preventive steps" that can keep children from becoming infected, such as vaccination against pneumococcus and good hygiene, Dr. Huang added. "The vaccine is very effective and prevents infection. In addition, wash [children's] hands and encourage their friends to wash their hands." Toys should also be cleaned regularly to reduce the risk of infection among playmates.

Calling the pneumococcal model "a highly simplified version of life," Dr. Huang emphasized that there are many factors that can potentially influence a community's level of pneumococcal carriage. "The model provides one hypothesis as to why some communities have a low percent of carriage in young children and other communities have a high percent of carriage," Dr. Huang said.