At Junction City Elementary School in Kentucky, the Swine Flu has followed students back to school.
Despite efforts to clean the school, there is at least one confirmed case of the H1N1 Virus.
By day's end Monday, more than a quarter of the school's students and staff were home, many of them reporting fever, vomiting and sore throat.
"You can't have school if you have that many people out so I mean its not a good thing. There's something definitely going around," said parent, Chris Gay.
Expecting more cases like this, at schools and in workplaces this fall, today the Obama Administration advises employers on how to prepare for it.
"Obviously everybody's kind of holding their breath here about the timing knowing that this is seriously a virus that seems to have very high infectivity,” said NIH Director, Francis Collins.
45 million doses of an H1N1 vaccine are expected to be ready by October. The start of planned mass vaccinations.
"We're going to encourage all those people to think about where they are going to get their vaccine and start making plans for that knowing that the additional doses will be coming in after that," said Dr. Bruce Gellin of the National Vaccine Program.
Experts stress that aside from shots, there are things people can do to protect themselves.
"Make sure you ride your kids, soap and water under the sink, singing happy birthday as many times as they can during the day," said NBC Medical Expert Dr. Nancy Snyderman.
H1N1 affects more young people than the seasonal flu. That means more people are vulnerable.