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The flu could be infecting more people than the numbers reveal. According to a new study, over the past few years, around three-quarters of people were infected with the seasonal flu and the swine flu but did not exhibit any kinds of symptoms or had mild symptoms that did not require medical attention.

"[The] flu is more common than we thought, but often less severe than what we had thought," stated lead author, Andrew Hayward, an epidemiologist from the University College London according to NPR.

The study's researchers examined data collected during the winter flu seasons from 2006 though to 2011. The data came from England and included the 2009 H1N1 swine flu season. The team had collected blood samples before and after the winter flu season every year. The researchers also followed up on the participants by interviewing them about any symptoms, such as a cough, sore throat or a cold. Participants who experienced flu-like symptoms throughout the winter had submitted nasal swabs.

The team calculated that even though 18 percent of the unvaccinated individuals were technically infected with an influenza virus, only 23 percent of that group developed symptoms. Out of the 23 percent, only around 17 percent sought out medical care due to the severity of their symptoms.

"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," Hayward said according Philly. "Most people don't go to the doctor when they have flu. 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."

The researchers stressed the importance of determining whether or not these mild cases of influenza could be infectious and how that could affect flu rates. The report was published in The Lancet Respiratory Medicine.