“It's uncertain right now how severe this outbreak will be in terms of the ultimate illness and mortality toll that it takes, or whether this virus will turn out to be worse than others that we've handled through the seasonal flu experience,” said Dr. Anne Schuchat of the CDC's Immunization and Respiratory Disease Center during a teleconference with reporters on May 18. “Things could change quickly, and we do continue our efforts to prepare, particularly for the fall, where history tells us we might have a second wave of this new virus.”

As of May 4, more than 1,000 confirmed or probable cases of novel influenza A (H1N1) were reported from 44 states. The CDC and other government agencies have relaxed travel advisories for U.S. citizens visiting Mexico and are no longer advising schools and child care programs close in response to either suspected or confirmed cases. In addition to following sanitary measures, affected students and school faculty and staff should stay home for at least seven days. Earlier this month, Dr. Margaret Chan, the director-general of the World Health Organization, said the alert level remains at five and warned that, although initially mild, H1N1 could still take a turn for the worse.

Schuchat said the trend continues to be that more children and teens have been affected.

“What we see in the data so far is that the people under 18 are more likely to have the infection when another person in the family is infected,” she said. “The transmission is a bit more active in the younger population than in the older population. They have lots of social contacts, and in particular, younger children may shed the virus for a longer time. Of course, the alternate hypothesis is that it just may take longer for this virus to make its way into the senior population. If kids hang around with other kids, and seniors hang around with other seniors, and the virus is really spreading rapidly among the kids, it just may take a bit of time, and then it may enter that senior population more aggressively than it has so far.”

An ongoing STN Web Poll has found that about one-third of respondents so far indicate they are disinfecting school buses on a daily basis. But Susan F. Wooley of the American School Health Association said there has yet to be scientific evidence to say daily swabs make a difference because of the airborne qualities of the virus.

“It's more important to be getting kids to wash their hands and use hand sanitizer; it may even be more effective that the bus driver have a bottle of hand sanitizer,” she said. “In a closed environment like a bus, if a kid is coughing and happens to have it , the kids near them are going to be inhaling that whether you're disinfecting the surface or not.”