Airport quarantine inspection, follow-up observation, and the prevention of pandemic influenza.

INTRODUCTION

After a report of H1N1 novel influenza in Mexico and North America, Japan conducted onboard quarantine inspections from late April 2009. The detection rate in border quarantine inspection is low due to incubation period and thus inspection is considered to be ineffective in blocking the entry of influenza. However, little is known about the concomitant effects of such inspection, such as increased traceability, upon secondary transmission.

METHODS

Epidemiological data were collected from the web sites of the Department of Health, Labor, and Welfare of Japan and the National Institute of Infectious Diseases of Japan. The number of weekly patients with H1N1 pandemic influenza in eight districts of Japan was summarized. The number of patients who passed through quarantine inspection at the airports was also calculated. A person with overseas travel history was defined as a person who had a flight only from the United States, Canada, or Mexico and passed through the quarantine inspection (according to the quarantine policy of the Japanese government). The numbers were adjusted for the population of each district and expressed as the number of patients per one million people.

RESULTS

Despite Kanto district having the largest population, the number of patients with H1N1 novel influenza was relatively small. The total number of cases in each district correlated inversely to the percentage of cases with airport quarantine inspection.

DISCUSSION

Quarantine inspection at the airports, follow-up observation by local authorities, and overall concomitant efforts may have contributed to secondary infection control in Japan.