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Study: flu infection often goes unnoticed

Study: flu infection often goes unnoticed

Influenza is without symptoms in three quarters of the cases

18.03.2014
For most people, the so-called "real" flu is characterized by sudden fever, chills, body aches and severe cold symptoms such as cough, runny nose and sore throat. In fact, according to a recent British study, only a quarter of patients have this type of influenza - in all other cases, however, no disease symptoms develop.

Flu often comes as a surprise with severe symptoms. Those who become infected with influenza viruses often develop symptoms such as fever with simultaneous chills and suddenly feel extremely sick and weakened. Here, strict bed rest and protection is usually indicated, so that the disease can heal quickly, as further measures are possible - depending on the existing symptoms - for example pain medication, inhalations or various home remedies for fever. Given the severe complaints, many people are concerned about real flu - but, as British researchers have now discovered, only a small proportion of the cases seem to be as difficult at all. In 75% of the patients infected with influenza viruses, however, the disease would be asymptomatic, report Andrew Hayward and his team of researchers from University College London in the journal "The Lancet Respiratory Medicine".

Several hundred households in England accompanied by flu season For their study, the researchers examined several hundred households in England from 2006 to 2011 during the flu season and took blood samples from the test subjects in spring and autumn, and this week after week according to their state of health questioned. In addition, the participants were asked to submit a nasal swab in the event of a cold symptom for further examinations, in order to be able to derive from the sum of the information who actually got infected and how the disease had progressed in individual cases. The scientists came to a surprising result: Although every winter an average of 18 percent of the non-vaccinated participants were infected with influenza viruses, only a quarter of those affected showed signs of illness at all. The majority of the subjects, on the other hand, had no complaints and therefore did not even notice that they had been infected.

Many cases of swine flu remain undetected Also in 2009, when the H1N1 virus or the so-called "swine flu" spread rapidly in England, the researchers had an equally high proportion of undetected cases: "Seasonal flu and the Pandemic strains from 2009 were characterized by a similarly high proportion of mainly asymptomatic infections. The 2009 pandemic strain even caused milder symptoms in the population than seasonal H3N2 flu, ”the authors said in their article. Accordingly, even after a small proportion of those affected, the researchers visited a doctor despite being infected - which led to the conclusion that previous flu statistics based on family doctor data would greatly underestimate the actual extent of the infections.

Only 16 out of 93 people with confirmed influenza go to their family doctor. “Most people with influenza confirmed by the PCR test did not see a doctor, and among those who did, influenza or flu-like illness was rarely medically documented. Medical review of 93 PCR-confirmed influenza cases in all seasons and 459 episodes of influenza-like illness showed that 16 out of 93 people with PCR-confirmed influenza (17%) and 96 out of 459 people with influenza-like Disease (21%) had consulted their GP, ”the researchers continued.

Contagion risk from asymptomatic infections far higher than previously assumed Despite the often mild or absent signs of the disease, the flu cannot be downplayed by the scientists. On the contrary, because precisely because three quarters of the cases remained undetected, the risk of infection is far higher than previously thought. Accordingly, according to Andrew Hayward, it is precisely these asymptomatic infections that need to be clearly taken into account as part of prevention in order to be able to better and more effectively cope with major influenza pandemics. (No)

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