People suffering from influenza may be at six-fold increased risk of experiencing a heart attack, particularly in first seven days, warned a study emphasising the importance of vaccination.

The risk may be higher for older adults, patients with influenza B infections, and patients experiencing their first heart attack. "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 Institute for Clinical Evaluative Sciences (ICES) -- Canada-based non-profit.

"The study, combined with previous evidence that influenza vaccination reduces cardiovascular events and mortality, support international guidelines that advocate for influenza immunisation in those at high risk of a heart attack," Kwong added.

In the study, published in the New England Journal of Medicine, the researchers identified 332 patients from 2009 to 2014 who were hospitalised for a heart attack within one year of a laboratory-confirmed influenza diagnosis. They found a significant association between acute respiratory infections, particularly influenza, and acute myocardial infarction. However, the risk was not as high with infection from other respiratory viruses.

As per World Health Organisation (WHO) estimates seasonal influenza outbreaks each year cause three million to five million severe cases and 300,000 to 500,000 deaths globally. In 2017, India had 38,220 cases and 2,186 deaths from H1N1, compared to 1,786 cases and 265 deaths in 2016.

According to the Centers for Disease Control and Prevention (CDC), flu season in 2018 has been unusually active and is still spreading in the US. While over 60,000 samples testing positive for influenza have been reported since monitoring for the virus began on October 1, a total of 30 children have died from in 2018 in the US, the CDC said. "People at risk of heart disease should take precautions to prevent respiratory infections, and especially influenza, through measures including vaccinations and handwashing," Kwong suggested.