The incubation period for novel H1N1 2009 infection appears to range from 2 to 7 days; however, additional information is needed. On the basis of data regarding viral shedding from studies of seasonal infl uenza, most patients with novel H1N1 2009 infection might shed virus from 1 day before the onset of symptoms through 5 to 7 days after the onset of symptoms or until symptoms resolve; in young children and in immunocompromised or severely ill patients, the infectious period might be longer [12] . Patients who are at highest risk for severe complications of novel H1N1 2009 infection are likely to include but may not be limited to groups at highest risk for severe seasonal infl uenza: children under the age of 5 years, adults 65 years of age or older, children and adults of any age with underlying chronic medical conditions and pregnant women [13] .