US health officials estimate that at least one million Americans have been infected with swine flu since the H1N1 virus emerged nearly three months ago.
The number is far higher than cases actually reported to the authorities.
The Centers for Disease Control and Prevention (CDC) said many cases were mild, although 127 people had died.
The CDC based its figures on surveys, rather than laboratory evidence, but the numbers suggest the death rate from swine flu is lower than thought.
"We're saying that there have been at least a million cases of the new H1N1 virus so far this year in the United States," said Anne Schuchat of the CDC.
"Reported cases are really just the tip of the iceberg."
The CDC has based its estimate on mathematical modelling, based on surveys by health officials.
If the figures are correct, it is reassuring news, because it indicates that the fatality rate from swine flu is even lower than thought, says BBC medical correspondent Fergus Walsh.
However, Dr Schuchat warned that swine flu might exhibit higher infection rates than seasonal flu and could return in a more virulent form in the autumn.
Argentina election
According to the CDC, there have been 27,717 confirmed or probable cases; some 3,000 people have needed hospital treatment and there have been 127 deaths.
Swine flu continues to affect mainly people under 50 years of age, with many of those worst affected having underlying health problems such as asthma or diabetes.
The average age of those who died in the US is 37.
Officials from the CDC and the World Health Organization are watching outbreaks in the southern hemisphere, in particular in Argentina, Chile and Australia, to see how the H1N1 virus has been spreading during the winter months and whether it is likely to become more virulent.
Argentina's health ministry has registered 26 deaths attributed to swine flu, and 1,587 cases. Officials are advising people to try to leave space between each other as they line up to vote in legislative elections on Sunday.
Chilean health authorities say there have been 6,211 cases and 12 deaths.
In Australia, there have been five swine-flu related deaths, all of patients with existing medical conditions, and 3,677 cases, according to official figures.
The H1N1 virus first emerged in April in Mexico, which has recorded 116 deaths and 8,279 cases, according to the WHO.
On 11 June, the WHO declared a global flu pandemic, meaning that swine flu virus was spreading in at least two regions of the world.
Officials stressed that this did not mean the virus was causing more severe illness or more deaths.
According to the latest figures from the WHO, there have been 263 deaths and nearly 60,000 cases in some 100 countries and territories.
Animal fats pancreas cancer link
Eating a diet high in red meat and dairy products is linked to an increased risk of pancreatic cancer, a US study has suggested.
Researchers followed 500,000 people who had completed a food diary for an average of six years.
The Journal of the National Cancer Institute paper found those who had the most animal fats in their diet had a higher risk of developing the cancer.
UK experts said cutting down on the fats was a way of reducing risk.
There has previously been confusion over whether there was a link between animal fats and pancreatic cancer, with different studies reaching opposite conclusions.
About 7,000 people are diagnosed with pancreatic cancer in the UK each year, with smoking being the biggest risk factor.
The prognosis is poor - the time between diagnosis and death is usually about six months.
'Welcome addition'
This latest research was carried out by the National Cancer Institute in Bethesda, Maryland, which felt earlier studies had been too small to give reliable results.
The participants were being followed to see if they developed a range of diseases.
Of the half a million studied, 1,337 developed pancreatic cancer.
Men who consumed the highest amount of total fats had a 53% higher relative rate of pancreatic cancer compared with men who ate the least.
In women, there was a 23% higher rate of the disease in those eating the most fat compared with those who ate the least.
Overall, people who consumed high amounts of saturated fats had 36% higher relative rates of pancreatic cancer compared with those who consumed low amounts.
Writing in the Journal of the National Cancer Institute, the researchers led by Dr Rachel Stolzenberg-Solomon, said: "We observed positive associations between pancreatic cancer and intakes of total, saturated, and monounsaturated fat overall, particularly from red meat and dairy food sources.
"We did not observe any consistent association with polyunsaturated or fat from plant food sources.
"Altogether, these results suggest a role for animal fat in pancreatic carcinogenesis."
In an editorial in the journal, Dr Brian Wolpin, of the Dana Farber Cancer Institute in Boston, and Dr Meir Stampfer, of the Harvard School of Public Health, said the study was a "welcome addition to the understanding of a disease that is in great need of new insights".
Josephine Querido, senior science information officer for Cancer Research UK, said: "This large study adds to the evidence that pancreatic cancer is more common in people who eat too much fat, particularly saturated fat.
"Understanding ways of reducing the risk of pancreatic cancer is very important because it can be very difficult to treat.
"Apart from stopping smoking, the best way to reduce your risk of cancer is to eat plenty of fruit vegetables and fibre, and to cut down on fatty foods, red and processed meat and limit your intake of alcohol."
Colon Cancer Awareness
SYRACUSE - March is National Colorectal Cancer Awareness Month. It's the third leading cause of cancer death in both men and women. But you can survive it and early detection is key.
Say the word colonoscopy and you'll probably see people scurry. Colon cancer screening isn't something many people look forward to, but it could save your life. "I think nobody likes to talk about their bowel habits and that part of the body is kind of taboo," said Martha Ryan of the American Cancer Society. "I think the issue is that people really need to get over that. Twenty years ago, people thought the same thing about breast cancer," she said.
For Martha Ryan, this all hits close to home. Her dad is a colon cancer survivor. Now, she's trying to help others survive too. If every person across the country age 50 and older got screened for colon cancer, more than 26,000 lives could be saved every year.
The reality is that only about half of them are getting tested. To blame is a lack of access to quality health care, lack of insurance and lack of knowledge about the importance of screening. "That should be no excuse because in New York State, we have the Cancer Services Program and it's in every single county in New York State," Ryan said. That means any uninsured or under insured New Yorker can get screened for free.
Locally, the American Cancer Society is trying to get the word out to make sure everyone who need a colonoscopy gets one. Here's what puts you at risk: Being overweight. Studies show you're more likely to develop colon cancer and die from it if you don't watch your waistline. A diet high in red or processed meat is also known to increase your risk. Your chances also increase with age. More than 90% of people diagnosed are 50 and older. And if you have a family history of colon cancer, that also increases your odds of developing the disease. "If your family member has colon cancer, you need to remember that you should be screened 10 years prior to when they were diagnosed," Ryan said.
Studies show high levels of physical activity may cut your risk of colon cancer in half. So, exercise for 30 minutes per day, five or more days a week. And stock up on a healthy diet, filled with whole grains, fruits and vegetables. And most importantly, get screened if you're 50 and older or if you have a family history.
US health officials estimate that at least one million Americans have been infected with swine flu since the H1N1 virus emerged nearly three months ago.
Eating a diet high in red meat and dairy products is linked to an increased risk of pancreatic cancer, a US study has suggested.
SYRACUSE - March is National Colorectal Cancer Awareness Month. It's the third leading cause of cancer death in both men and women. But you can survive it and early detection is key.