Marc Lipsitch

"The control of SARS was a tremendous public health success," said Marc Lipsitch, associate professor of epidemiology in the Department of Epidemiology. "But overall, the sum total of control for SARS was barely adequate. Flu is a considerably harder problem. The fact that we barely controlled SARS is not at all reassuring."

Every year in this country, the flu already kills about 40,000 vulnerable people. If history is a guide, the planet is due for a more lethal strain that will spread quickly between people, Lipsitch said. In a recent list of a dozen anticipated disaster scenarios, homeland security officials rated pandemic flu as the most likely.

The most severe recent pandemic of 1918-19 killed about two percent of the people it infected, causing millions of deaths worldwide. Lipsitch co-authored an analysis in the December 16, 2004 issue of Nature.

Now, public health officials are keeping a wary eye on a vicious strain of influenza, known as the H5N1 virus, in domestic and wild poultry in Southeast Asia. In the last two years, the bird flu has infected people in eight Southeast Asian countries, causing 52 deaths among the 89 known cases, Lipsitch said.

Officials had believed that transmission was limited to bird to human, with very limited human-to-human transmission. But, just days after the HSPH symposium, the World Health Organization issued a paper that said the pattern of avian flu found in northern Vietnam is consistent with human-to-human transmission. Further study is needed.

Gabriel Leung

To minimize the potentially hazardous mixing of viruses between people and birds, Hong Kong officials have instituted "rest days" at the markets two times a month, when all unsold birds are culled, and the markets are completely washed down. These efforts help to dramatically reduce viral load counts in chickens tested for influenza strains and to interrupt the "amplification" effect of such retail markets.

Next, government officials are hoping to introduce a few regional slaughterhouses. Less popular is the idea of a central slaughtering house that ships prepared chilled meat to stores. The idea has not been embraced, mostly due to strong local culinary preference for fresh meat, Leung explained.

Using SARS as Guide

To help prepare for a possible flu pandemic, public health officials are examining a recent epidemic scare-SARS. When the virus hit Hong Kong two years ago, health experts first thought it was the avian flu turning into the predicted pandemic.

"With SARS we were lucky," Leung said. "It is not infectious until the fever and symptoms appear, by which time we have a chance to isolate people. Then it becomes a hospital control problem, not a community control problem. The flu is much more difficult to deal with in terms of syndromic surveillance. A substantial proportion of people transmit the virus before they get symptoms."

Hong Kong officials tracked cases and contacts through a special SARS module that was superimposed over an existing citywide hospital network, with links to the University of Hong Kong and a disease control agency. Scientists could then evaluate the information for new clues about how to curb the spread of the disease.

	Gerilynne Nephew

He died on March 13. By then four other family members had been admitted to different hospitals. The next day, Toronto Public Health announced that SARS had arrived.

Toronto health officials did not know the identity of the infectious agent, how it moved from person to person, and how long after infection did symptoms appear. They had no diagnostic test, no prophylactic drugs, no vaccine, and no treatment.

"We resorted to the old-fashioned quarantine," Nephew said. "In Canada, quarantine had not been used in 50 years."

Most people voluntarily quarantined themselves at home when asked, she said, despite the emotional, physical, and financial difficulties. Infected or exposed people were asked to stay away from other family members in the house. Public health staff checked in daily by phone.

For the 14-week emergency, officials worked with color-coded files, ultimately investigating 2,035 possible cases, following up on 26,000 contacts, and quarantining thousands of people, Nephew said. They eventually developed a data management system called the Case and Contact Management System, which became operational toward the end of the outbreak.

All of the speakers emphasized the need for a flexible informatics infrastructure for detecting cases and monitoring the progress of the virus and the disease.

Communications is a key component of the response. In the media, the SARS story was second only to the Iraq war, said Nephew. Live televised media briefings every afternoon were supplemented by a hotline for patients and caregivers that fielded 300,000 calls, fact sheets in print and on the Web in 14 languages, local community meetings, and directives to specific groups. Different spokespeople with different opinions, such as whether or not to wear a mask, can leave the public confused, Nephew and Leung said.

In developing a flu pandemic plan for Toronto, Nephew is anticipating that about one-third of health care workers will be sick or unable to work because they are caring for someone sick. The first round of the limited antiviral medicine they are now stockpiling will go to health workers and city personnel essential to infrastructure, such as water, power, and emergency workers.

"Pandemic flu planning can become overwhelming when you think about the impact," Nephew said. "It's important to share the message and to bring the multisector stakeholders to the table so you're making plans together."

--CCM