Introduction: Since late March 2009, a novel influenza H1N1 strain emerged in humans in Mexico and the United States. It has rapidly spread to many countries on different continents, prompting unprecedented activation of pandemic preparedness plans. Singapore has adopted a containment strategy with active screening of febrile travellers with respiratory symptoms from affected countries since April 27, 2009.
Methods: All cases with new influenza A (H1N1) confirmed on polymerase chain reaction assay on combined nasal and throat swabs and who were admitted to the Communicable Disease Centre, were included in a prospective evaluation of clinical characteristics of new influenza A (H1N1).
Results: From May 26 to June 3, 2009, there were ten patients with a mean age of 27.6 years, seven of whom were female. All but one travelled from the United States, six of whom travelled from New York; the last one travelled from the Philippines. Clinical illness developed within a mean of 1.4 days after arrival in Singapore, and presentation to the emergency department at a mean of 2.7 days from illness onset. Fever occurred in 90 percent, cough 70 percent, coryza 40 percent, sore throat and myalgia/arthralgia 30 percent; none had diarrhoea. The fever lasted a mean of 2.1 days. All were treated with oseltamivir. The clinical course was uncomplicated in all cases.
Conclusion: Clinical features of new influenza A (H1N1) appeared mild, and ran an uncomplicated course in immunocompetent patients.