WASHINGTON, Jan. 24 (Xinhua) -- The risk of a heart attack may be increased six-fold within the first week after detection of laboratory-confirmed influenza infection, a new study said Wednesday.

Researchers in Canada looked at nearly 20,000 Ontario adult cases of laboratory-confirmed influenza infection from 2009 to 2014 and identified 332 patients who were hospitalized for a heart attack within one year of flu diagnosis.

They found a significant association between acute respiratory infections, particularly flu, and acute myocardial infarction, according to the study published in the New England Journal of Medicine.

The risk may be higher for older adults, patients with influenza B infections, and patients experiencing their first heart attack.

The researchers also found elevated risk, albeit not as high as for flu, with infection from other respiratory viruses.

"Our findings are important because an association between influenza and acute myocardial infarction reinforces the importance of vaccination," said lead author Jeff Kwong, a scientist at the Institute for Clinical Evaluative Sciences (ICES) and Public Health Ontario (PHO).

"People at risk of heart disease should take precautions to prevent respiratory infections, and especially influenza, through measures including vaccinations and handwashing," said Kwong.

The researchers added that patients should not delay medical evaluation for heart symptoms particularly within the first week of an acute respiratory infection.