Japan, India, and China were among the nations that attempted to identify and interdict those who might be carrying the H1N1 virus when they entered their country.
While their efforts may have slowed the introduction of the virus, they certainly didn’t stop it.
And a study today out of Japan suggests that between asymptomatic or mild infections, and a silent incubation period of several days, there wasn’t much chance of long-term success.
For every person identified, and quarantined, by port authorities - researchers estimate 14 others infected by the virus entered undetected.
First a article from The Yomiuri Shimbun, followed by a link to the study which appears in Eurosurveillance.
The Yomiuri Shimbun
The number of people infected with new flu who passed undetected through airport quarantine between April last year, when the new strain of influenza began spreading, and May was about 14 times higher than the number of infected people stopped at the airports, according to a study carried out by Tokyo University.
The research results confirm anew that to prepare for an outbreak of new infectious diseases, such as bird flu, it is essential to take comprehensive countermeasures, such as having medical institutions prepare to treat large numbers of patients and closing schools, in addition to quarantine, from the early stage of proliferation of such a disease.
An official of the Health, Labor and Welfare Ministry said, "We'll use the data to work out to what extent quarantine measures [at ports] can prevent new infectious diseases from entering the nation."
The research results were to be published Thursday in the online version of Eurosurveillance, a European journal on infectious disease prevention.
Most of the infected people who passed through quarantine undetected were experiencing the incubation stage of new flu, in which fever and other noticeable symptoms do not appear.
Eurosurveillance, Volume 15, Issue 1, 07 January 2010
H Sato , H Nakada, R Yamaguchi, S Imoto, S Miyano, M Kami
We simulated the early phase of the 2009 influenza A(H1N1) pandemic and assessed the effectiveness of public health interventions in Japan.
We show that the detection rate of border quarantine was low and the timing of the intervention was the most important factor involved in the control of the pandemic, with the maximum reduction in daily cases obtained after interventions started on day 6 or 11.
Early interventions were not always effective.
Last month we looked at the failure of thermal scanners to detect those with fevers from entering Singapore in Travel-Associated H1N1 Influenza in Singapore and last summer I wrote about ways passengers were defeating the scanners to get home in Vietnam Discovers Passengers Beating Thermal Scanners.
Areas that receive a small number of arrivals might be able to institute a quarantine system (see Can Island Nations Effectively Quarantine Against Pandemic Flu? ), but even then the ability to interdict infected travelers won’t be 100%.
The four successful quarantines during the 1918 pandemic were in American Samoa (5 days' quarantine) and Continental Australia, Tasmania, and New Caledonia (all 7 days' quarantine).
- The Spanish Flu did not reach American Samoa until 1920, and had apparently weakened, as no deaths were reported.
- Australia's quarantine kept the influenza away until January of 1919, a full 3 months after the flu has swept New Zealand with disastrous effects.
- Tasmania kept the flu at bay until August of 1919, and health officials believed they received an milder version, as their mortality rate was one of the lowest in the world.
- By strictly enforcing a 7-day quarantine, New Caledonia managed to avoid introduction of the virus until 1921.
Eventually, once the quarantines were lifted, the virus did make it to these isolated regions of the world.