Yesterday, federal health officials urged Americans to be vigilant against swine flu.   Stating that the virus seems to be milder disease yet could still be a serious threat to the health of certain individuals.
Richard E. Besser, acting director of the federal Centers for Disease Control is concerned that Americans could wrongly believe the worse is over.
U.S. confirmed 1639 cases in 42 states and the District, an increase of 743 cases a day earlier.
This increase is mainly due to further testing, but more accurately, it is clear that people are still infected. At least 57 Americans were in the hospital, including 26 who also had another condition.
U.S. Department of Education said more than 81,000 students returned to class yesterday, 155 schools re-opened. At least 166 schools were closed, but federal officials have stated that they expect all students back in class on Tuesday.
Influenza H1N1 has infected 3440 people in 29 countries, the World Health Organization (WHO) said on Saturday.  45 people have died from the new strain of flu, a mixture pigs, birds and human viruses.