Sensation makes headlining news but not good science

The award for the most sensational swine flu story goes to The Age. The number of swine flu victims in Australia was overstated by 5,500–fold.

Today’s news headlined: “One-third of Victorians may have flu.” According to the story, “up to one-third of Victorians could now be infected with swine flu, an expert said yesterday, as the Federal Government announced it was preparing to ramp up its response to the virus in coming days.” Last night, Health Minister Nicola Roxon was reported as saying that the total number of people in Australia infected with the swine flu had hit 1,515.

Fact check: This equals about 0.006% of the Australian population — the Australian population was 21,814,135 people as of June 15, 2009, 12:26am, according to the Australia Bureau of Statistics.

Health surveillance finding about 0.006% of the Australian population infected with swine flu is a far cry from one in three, 33.33%, as is being claimed. Even if every single case of swine flu in Australia came from Victoria, that would only represent 0.028% of the Victorian population (5,364,800 people per Australia Bureau of Statistics).

Who were the experts suggesting that one-third of the Victorian population could now have swine flu? The Age reported:

Professor Greg Tannock, a virologist from the Burnet Institute, said that although it was difficult to estimate, up to one in three people could have picked up the virus by now. "I think one in three is a reasonable estimate, but that's based on sheer gut feeling rather than anything else. We need hard data," he said.

President of the Australian Medical Association Victoria, Dr Harry Hemley, said doctors had been inundated with people suffering respiratory infections, including whooping cough and influenza that could be the H1N1 virus, in recent weeks. "I would say about one-third of the population has some sort of upper respiratory infection right now, but I can't say how many of those have swine flu," he said.

More frightening than the swine flu is the fact medical experts would fall for the Land of Incognita fallacy. Reports of more flu-like symptoms being seen at clinics and emergency rooms is an indication of swine flu panic, not actual disease. Nor has there been any death from swine flu reported in Australia, according to the World Health Organization.

But Health Minister Roxon also repeated another faulty statistic, linking obesity to a greater risk for swine flu. The source of the claim that obesity is a risk factor for swine flu is the May 22^nd CDC Morbidity and Mortality Weekly Report about hospitalized cases of H1N1 seen in California from April to May. The MMWR report was released online on May 18^th and was covered in a widely syndicated article in the Washington Post titled: “Survey Finds Link Between Obesity and Flu Severity.” According to the newspaper, the CDC report suggested that obesity could be as much of a risk factor for serious complications from the flu as diabetes, heart disease and pregnancy.

“We were surprised by the frequency of obesity among the severe cases that we've been tracking,” CDC epidemiologist Dr. Anne Schuchat was quoted as saying. The Washington Post said scientists are “looking into the possibility that obese people should be at the head of the line along with other high-risk groups if a swine flu vaccine becomes available.”

The claim that obesity is a risk factor for swine flu has since spread around the world in more than 816,000 stories over the past month. News stories are reporting that obesity is one of the conditions that puts people at greater risk.

We can’t count on newspaper journalists or even medical experts and government officials to do much in the way of fact checking or to clarify the information. Going to the original source finds that the CDC had actually reported that four out of the 30 patients hospitalized in California for H1N1 had been obese — that’s 13%. According to the CDC National Center for Health Statistic, 34% of Americans are obese — which means fat people are decidedly under-represented among those hospitalized for the flu. Obesity would appear protective.

Looking more closely at the CDC report finds that most hospitalized cases occurred in people with other health problems. Among those obese patients were: two asthmatics (a 7 year old and a 40 year old who also had hypertension), a 30 year old diabetic, and a 41 year old patient with autoimmune hepatitis/biliary cirrhosis and liver transplant who was also hypertensive. The text of the report also described an 87 year old woman with multiple medical problems, including breast cancer with possible abdominal metastasis, hypertension, diabetes mellitus, coronary artery disease, cerebrovascular disease, chronic renal insufficiency… and obesity.

The obesity link has taken on a life of its own because few people understand what risk factor means. As we know, it means nothing more than that a correlation was found. Risk factor is not the same thing as a risk. But the correlation with obesity led many people to believe that obesity has a causal role and increases the risks of swine flu. And another obesity scare is born.