Flu can infect many without causing symptoms - NewsChannel5.com | Nashville News, Weather & Sports

Flu can infect many without causing symptoms

Updated: March 17, 2014 09:13 AM
© iStockphoto.com / Nick Schlax © iStockphoto.com / Nick Schlax

SUNDAY, March 16, 2014 (HealthDay News) -- Think you know who has the flu? Think again: a new study finds that three-quarters of people infected with seasonal flu and swine flu in recent years showed no symptoms.

Researchers analyzed data gathered in England during the winter flu seasons between 2006 and 2011, including the 2009 H1N1 "swine flu" pandemic.

Overall, about 18 percent of unvaccinated people became infected with an influenza virus, but only 23 percent of them went on to develop flu symptoms, the researchers reported March 16 in The Lancet Respiratory Medicine.

What's more, only about 17 percent of infected people became ill enough to see a doctor, the British study found. And compared with some of the seasonal flu strains, the 2009 swine flu strain actually caused much milder symptoms.

The findings suggest that relying on data about flu-related visits to primary care doctors underestimates the extent of flu infections and illnesses, the researchers said.

Overall, the infection rate for the winter flu seasons as calculated in the study were an average of 22 times higher than the rates recorded by standard methods.

"Reported cases of influenza represent the tip of a large clinical and subclinical iceberg that is mainly invisible to national surveillance systems that only record cases seeking medical attention," study lead author Dr. Andrew Hayward, of University College London, said in a journal news release.

"Most people don't go to the doctor when they have flu," he added. "Even when they do consult they are often not recognized as having influenza. Surveillance based on patients who consult greatly underestimates the number of community cases, which in turn can lead to overestimates of the proportion of cases who end up in hospital or die."

An important question that needs to be answered is whether people who have the flu but have only mild or no symptoms can still easily pass on the virus, Dr. Peter William Horby from the Oxford University Clinical Research Unit in Vietnam, wrote in an accompanying editorial.

Even if only mildly infectious, a large number of these people could play a major role in spreading flu each season, he suggested.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about influenza.

Copyright © 2014 HealthDay. All rights reserved.

  • Medical News HeadlinesMedical News HeadlinesMore>>

  • Could Down Syndrome Be The Key To Alzheimer's?

    Could Down Syndrome Be The Key To Alzheimer's?

    Monday, July 21 2014 5:15 PM EDT2014-07-21 21:15:13 GMT
    More than five million Americans are living with Alzheimer’s. More than 400,000 of them also have Down syndrome. What does a condition seen at birth have in common with a disease typically diagnosed in the elderly? Quite a bit.more>>
    More than five million Americans are living with Alzheimer’s. More than 400,000 of them also have Down syndrome. What does a condition seen at birth have in common with a disease typically diagnosed in the elderly? Quite a bit.more>>
  • Extreme Workouts

    Extreme Workouts

    Friday, July 18 2014 6:04 PM EDT2014-07-18 22:04:23 GMT
    Workout routines have taken a tortuous turn. Running through mud and fighting in cages are just some of the latest extreme workouts, but one wrong move and you could be in trouble.more>>
    Workout routines have taken a tortuous turn. Running through mud and fighting in cages are just some of the latest extreme workouts, but one wrong move and you could be in trouble.more>>
  • Extreme Skin

    Extreme Skin

    Thursday, July 17 2014 5:15 PM EDT2014-07-17 21:15:05 GMT
    Last year, Americans underwent more than 11-million cosmetic procedures and spent nearly $12-billion on skin rejuvenation. Everyone wants their skin to look younger, healthier and better, but some are taking it to an extreme.more>>
    Last year, Americans underwent more than 11-million cosmetic procedures and spent nearly $12-billion on skin rejuvenation. Everyone wants their skin to look younger, healthier and better, but some are taking it to an extreme.more>>
  • Extreme Diets

    Extreme Diets

    Wednesday, July 16 2014 5:15 PM EDT2014-07-16 21:15:07 GMT
    Dieting is an American pastime. About 45-million of us diet each year, and we spend about $33-billion on weight-loss products. There are more ways to diet than ever and some are pretty extreme.more>>
    Dieting is an American pastime. About 45-million of us diet each year, and we spend about $33-billion on weight-loss products. There are more ways to diet than ever and some are pretty extreme.more>>
  • Frozen Lumpectomy For Prostate

    Frozen Lumpectomy For Prostate

    Tuesday, July 15 2014 5:15 PM EDT2014-07-15 21:15:08 GMT
    More than 230,000 men will be diagnosed with prostate cancer this year according to the American Cancer Society. In most cases, surgical removal of the gland is considered the gold standard of treatment, but results of a new study suggest a new treatment might benefit some patients.more>>
    More than 230,000 men will be diagnosed with prostate cancer this year according to the American Cancer Society. In most cases, surgical removal of the gland is considered the gold standard of treatment, but results of a new study suggest a new treatment might benefit some patients.more>>
  • Bariatric Surgery For Diabetes

    Bariatric Surgery For Diabetes

    Wednesday, July 9 2014 5:15 PM EDT2014-07-09 21:15:09 GMT
    Nearly 90 percent of people with type-two diabetes are obese and as more Americans gain weight, more will likely face a diabetes diagnosis. In fact, the American Diabetes Association predicts that one in three adults will have diabetes by the year 2050. For years, we’ve heard about weight loss surgery and its effect on diabetes. Now, a new study is showing how well the popular surgery is working to stop this serious disease.more>>
    Nearly 90 percent of people with type-two diabetes are obese and as more Americans gain weight, more will likely face a diabetes diagnosis. In fact, the American Diabetes Association predicts that one in three adults will have diabetes by the year 2050. For years, we’ve heard about weight loss surgery and its effect on diabetes. Now, a new study is showing how well the popular surgery is working to stop this serious disease.more>>
  • Ankle Replacement

    Ankle Replacement

    Tuesday, July 8 2014 5:15 PM EDT2014-07-08 21:15:10 GMT
    More than 50 million Americans suffer from some form of arthritis. Between 6 percent and 13 percent of them have ankle arthritis. These patients feel pain with every single step they take, but now ankle replacements are giving patients a new lease on life.more>>
    More than 50 million Americans suffer from some form of arthritis. Between 6 percent and 13 percent of them have ankle arthritis. These patients feel pain with every single step they take, but now ankle replacements are giving patients a new lease on life.more>>
  • 3D Knee

    3D Knee

    Monday, July 7 2014 5:15 PM EDT2014-07-07 21:15:09 GMT
    In the past ten years, the number of total knee replacements in the U.S. has doubled and many of those patients are much younger than ever before. Now, new technology allows doctors to make replacement knees that are the perfect fit.more>>
    In the past ten years, the number of total knee replacements in the U.S. has doubled and many of those patients are much younger than ever before. Now, new technology allows doctors to make replacement knees that are the perfect fit.more>>
  • Breath of Life for Heart Patients

    Breath of Life for Heart Patients

    Thursday, July 3 2014 6:20 PM EDT2014-07-03 22:20:13 GMT
    Heart failure, 5.7 million people in the U.S. have it and 55-thousand die from it each year. By definition, it means your heart cannot pump enough blood and oxygen to support all your other organs. Now, a simple breath test could make it easier and faster for doctors to diagnose.more>>
    Heart failure, 5.7 million people in the U.S. have it and 55-thousand die from it each year. By definition, it means your heart cannot pump enough blood and oxygen to support all your other organs. Now, a simple breath test could make it easier and faster for doctors to diagnose.more>>
  • Concave Chest In Teens

    Concave Chest In Teens

    Wednesday, July 2 2014 5:15 PM EDT2014-07-02 21:15:06 GMT
    Can you imagine being a teenage boy, living at the beach, and not having enough confidence to take your shirt off and not having enough energy to even take a walk? The condition is called concave chest. One-in-500 kids will be born with it.more>>
    Can you imagine being a teenage boy, living at the beach, and not having enough confidence to take your shirt off and not having enough energy to even take a walk? The condition is called concave chest. One-in-500 kids will be born with it.more>>
*DISCLAIMER*: The information contained in or provided through this site section is intended for general consumer understanding and education only and is not intended to be and is not a substitute for professional advice. Use of this site section and any information contained on or provided through this site section is at your own risk and any information contained on or provided through this site section is provided on an "as is" basis without any representations or warranties.
Powered by WorldNow
Powered by WorldNow
All content © Copyright 2000 - 2014 NewsChannel 5 (WTVF-TV) and WorldNow. All Rights Reserved.
For more information on this site, please read our Privacy Policy and Terms of Service.