Some Japanese analysts suspect that the virus somehow bypassed the entry quarantine inspection, infecting many local people.
Such inspection has also caused concern among some Chinese experts.(www.hXen.com)
They fear that a similar situation also exists in China as the country has confirmed several imported cases.
The Beijing News has published a commentary saying China should learn a lesson from Japan and further strengthen its own preventative measures.
The author says the origin-unidentified cases in Japan show that the flu virus might be incubated for a long time before being detected. It can infect others even during the incubation period.
The author suggests that the government spare no effort in expanding the monitoring net for the flu all over the country, and to set up more special laboratories and hospitals.
Only by such preventive measures, the author says, can we deter the flu from breaking out on a massive scale and spreading throughout the country.