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Web searches may have foreshadowed listeriosis crisis

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By Sharon Kirkey, Canwest News Service


Internet chatter foreshadowed the deadly outbreak of listeriosis a month before the first reports of death from the food-borne bacteria surfaced in Canada, a new analysis shows.

Who was searching for information about the disease and why, remain a mystery.

But researchers say Google searches for the term "listeriosis" demonstrated a possible signal of the outbreak linked to the death of 20 Canadians before the official announcement was made in Canada.

The public was officially told on Aug. 20, 2008 that a listeriosis outbreak had killed one person and had sickened 16 others.

But researchers from the University of Ottawa and Harvard Medical School found peak searching for the term "listeriosis" spiked beginning in mid to late July, "nearly a month before the declaration of the public outbreak," the team reports in an article released Thursday by the Canadian Medical Association Journal.

The term "listeriosis" is more technical than listeria. And peak searching for the word coincided with cases as they were occurring, as was confirmed later, and not with public announcements.

"In comparison, a massive increase in searching for the word 'Listeria' coincided perfectly with news media attention," write the authors.

Last summer's deadly outbreak was traced to ready-to-eat meats produced at a Maple Leaf Foods plant in Toronto. The company found listeria building up "deep inside" two slicing machines as the most likely source.

The Internet is "revolutionizing" how intelligence about epidemics and outbreaks is gathered, write Dr. Kumanan Wilson, of the Ottawa Health Research Institute and John Brownstein of Children's Hospital Boston. It's also making it more difficult for countries to hide or to suppress the full extent of an outbreak.

"There's all this massive amount of information that is being posted through a variety of different channels on the web blogs, chat rooms, news media sources that come outside of traditional public health," says Brownstein. The Montreal native is co-creator of HealthMap, a real-time, web-crawling system that pulls from more than 20,000 sources every hour for information on new and ongoing infectious disease outbreaks.

In November, Google launched Google Flu trends, which estimates how many people have a flu-like illness, based on the day's tally of flu-related search queries.

Health Canada's Global Public Health Intelligence Network identified the outbreak of SARS in Guangdong province in China as early as November 2002 more than two months before the World Health Organization published details on the cases.

"In the case of listeriosis, as soon as the outbreak was announced we saw people in Canada searching for the word "listeria'," Brownstein says. "That's not surprising. The media drives a lot of people's search habits on the web."

But searching for the more technical term "listeriosis" began about a month before the public announcement, "and peaked a couple of weeks before."

"We do know it wasn't just in one location, what we can see is that it was in a few different places in the country, so it wasn't like someone who was doing their PhD thesis alone caused the spike," says Wilson, Canada Research Chair at the University of Ottawa and Ottawa Health Research Institute.

It could have been food inspection or industry officials investigating the possibility of an outbreak. Or it could have been doctors, or relatives and friends of people infected early in the outbreak, or people concerned about the initial voluntary recalls, he said.

"The question that arises from this analysis is whether knowledge of this information, either by public health officials or members of the public, could have prompted an earlier response that may have reduced exposure to the contaminated products," write the authors.

"The problem is, this type of data can be highly noisy and set off lots of false signals," Brownstein said in an interview. "How much public health agencies can use this data still is in question. Is it really people who are getting sick? What do the data really reflect?"

Wilson says it will be up to public health and others to decide what's an acceptable false positive rate.

"If you're right even one out of 10 times, if that one time you're able to stop an outbreak that could kill a lot of people, it may be worth it."

The listeria signal "definitely would have suggested something that needed more investigation," Wilson says. "A signal like that could have prompted people to maybe look at this a little more carefully and thoroughly, and see, how much of a problem are we actually dealing with here?"



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