Flu pandemic impact can be mitigated in cities-study

HONG KONG, Aug 8 (Reuters) A densely populated city like Hong Kong can cut by half the number of infections in the first year of a flu pandemic using home quarantine, hospital isolation and antivirals, a study suggests.

Scientists from the University of Hong Kong assumed a fully fledged influenza pandemic in a city such as Hong Kong.

''We showed that with the combination of tried, tested public health interventions such as quarantine, isolation and antivirals, you could conceivably reduce the symptomatic attack rate from 49 percent all the way down to 27 percent,'' said Gabriel Leung, an associate professor at the university's School of Public Health.

Symptomatic attack rate is defined as the proportion of a population that is infected and showing symptoms. The scientists used Hong Kong's population of 6.8 million in their calculations.

Experts fear the H5N1 strain of bird flu, which made the first known jump to humans in Hong Kong in 1997, could mutate and become easily transmissible among people, triggering a pandemic that could kill millions of people.

Through home quarantine of household contacts of suspected cases, hospital isolation of symptomatic cases and antiviral therapy, Leung said symptomatic infections in a population such as Hong Kong's could be cut by half.

''That means about 16,000 fewer deaths if you assume a case fatality rate of about 1 percent, if you assume the New York experience in (the Spanish flu of) 1918,'' Leung said.

The study paints scenarios of what could happen at the peak of a pandemic, which in Hong Kong's case could mean 500,000 people in home quarantine -- a challenging prospect for any city government.

''During SARS (in Hong Kong), government people and police went to each quarantined household to deliver water, bread and so on, but this was because it was a very small number. But for 500,000 people, that would not be an option,'' Leung said.

''So should governments be thinking of neighbourhood depots with centralised supplies and people will come pick them up and you make sure that they wear proper precautions when they come out? We don't have all the answers but what we would like to do is to pose some questions,'' he said.

Severe Acute Respiratory Syndrome broke out in southern Guangdong province in 2002 and spread early in 2003, reaching several cities around the world and killing 774 people.

Leung said the mathematical model could be used for other big cities.

The study is to be published in the September issue of the open-access journal, the Public Library of Science; http://dx.doi.org/10.1371/journal.pmed.0030361.

There have been similar studies published in recent years, but these were confined to examining how influenza outbreaks in rural settings could be contained.

They have been criticised as unrealistic given the way nations such as Indonesia and China have handled bird flu.

H5N1 outbreaks have often gone unexamined, while human cases are not picked up until days later, by which time the virus could have spread to cities.

REUTERS DH RK0610