Winter viruses can trigger heart attack or stroke; time for a Covid shot
Winter is almost here, along with cold days and the inevitable seasonal surge in respiratory viruses. But it's not only the sniffles we need to worry about. Heart attacks and strokes also tend to rise during the winter months. In new research out this week we show one reason why. Our study shows catching common respiratory viruses raises your short-term risk of a heart attack or stroke. In other words, common viruses, such as those that cause flu and Covid, can trigger them. Wait, viruses can trigger heart attacks? Traditional risk factors such as smoking, high cholesterol, high blood pressure, diabetes, obesity and lack of exercise are the main reasons for heart attacks and strokes. And rates of heart attacks and strokes can rise in winter for several reasons.
Factors such as low temperature, less physical activity, more time spent indoors – perhaps with indoor air pollutants – can affect blood clotting and worsen the effects of traditional risk factors. But our new findings build on those from other researchers to show how respiratory viruses can also be a trigger. The theory is respiratory virus infections set off a heart attack or stroke, rather than directly cause them. If traditional risk factors are like dousing a house in petrol, the viral infection is like the matchstick that ignites the flame. For healthy, young people, a newer, well-kept house is unlikely to spontaneously combust. But an older or even abandoned house with faulty electric wiring needs just a spark to lead to a blaze. People who are particularly vulnerable to a heart attack or stroke triggered by a respiratory virus are those with more than one of those traditional risk factors, especially older people.
Our findings:
Our team conducted a meta-analysis (a study of existing studies) to see which respiratory viruses play a role in triggering heart attacks and strokes, and the strength of the link. This meant studying more than 11,000 scientific papers, spanning 40 years of research. Overall, the influenza virus and SARS-CoV-2 (the virus that causes COVID) were the main triggers.
If you catch the flu, we found the risk of a heart attack goes up almost 5.4 times and a stroke by 4.7 times compared with not being infected. The danger zone is short – within the first few days or weeks – and tapers off with time after being infected. Catching Covid can also trigger heart attacks and strokes, but there haven't been enough studies to say exactly what the increased risk is. We also found an increased risk of heart attacks or strokes with other viruses, including respiratory syncytial virus (RSV), enterovirus and cytomegalovirus. But the links are not as strong, probably because these viruses are less commonly detected or tested for.
What's going on?
Over a person's lifetime, our bodies wear and tear and the inside wall of our blood vessels becomes rough. Fatty build-ups (plaques) stick easily to these rough areas, inevitably accumulating and causing tight spaces. Generally, blood can still pass through, and these build-ups don't cause issues. Think of this as dousing the house in petrol, but it's not yet alright. So how does a viral infection act like a matchstick to ignite the flame? Through a cascading process of inflammation. High levels of inflammation that follow a viral infection can crack open a plaque. The body activates blood clotting to fix the crack but this clot could inadvertently block a blood vessel completely, causing a heart attack or stroke.
Some studies have found fragments of the COVID virus inside the blood clots that cause heart attacks – further evidence to back our findings. We don't know whether younger, healthier people are also at increased risk of a heart attack or stroke after infection with a respiratory virus. That's because people in the studies we analysed were almost always older adults with at least one of those traditional risk factors, so were already vulnerable. The bad news is we will all be vulnerable eventually, just by getting older.
What can be done?
The triggers we identified are mostly preventable by vaccination. There is good evidence from clinical trials that flu vaccines can reduce the risk of a heart attack or stroke, especially if someone already has heart problems. We aren't clear exactly how this works. But the theory is that avoiding common infections, or having less severe symptoms, reduces the chances of setting off the inflammatory chain reaction. Covid vaccination could also indirectly protect against heart attacks and strokes. But the evidence is still emerging.
(Tu Nguyen is with the University of Melbourne. Co-writer Christopher Reid is from Curtin University, while Diana Vlasenko, Hazel Clothier and Jim Buttery are from Murdoch Children's Research Institute)
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Time of India
4 hours ago
- Time of India
After uptick, Covid cases & deaths decline
New Delhi: After nearly a month of surge, Covid-19 cases and deaths due to the virus are on the decline. The number of active cases, which had crossed 7,000 on June 11, has declined to 4,425, govt data shows. One fatality was recorded in the last 24 hours in Nagpur. "Covid-19 is now endemic. It is not a serious threat. That's why many people aren't getting themselves tested even when symptoms surface," said a senior doctor. The virus is causing mild fever with most patients recovering at home in 2 to 3 days. "Only those with co-morbidities such as cancer, kidney disease and heart disease need to take extra care," the doctor added. Dr Rommel Tickoo, director of internal medicine at Max Saket, said: "We don't advise Covid tests for everyone with fever, cough and cold. But due to the panic and anxiety caused by a surge in cases in the last few weeks, some patients have come to us with positive Covid tests. Treatment involves symptomatic management and rest. In case of Covid or Covid-like symptoms, we also advise keeping away from others to check the spread of infection," he said. Dr Arjun Khanna, who heads pulmonology department at Amrita hospital, Faridabad, said that one new feature of the current wave is that Covid-19 has become clinically less distinct from other viral respiratory infections.
Time of India
4 hours ago
- Time of India
AIIMS Bhopal detects dominance of new XFG Covid variant, finds no trace of Nimbus strain
Bhopal: AIIMS Bhopal is reporting 'no detection' of NB.1 ( Nimbus variant ) in their sequenced samples from Madhya Pradesh, despite its classification as a 'Variant Under Monitoring' by the WHO. AIIMS Bhopal's data shows the early dominance of XFG in MP, while NB.1.8.1 is more prominent in other regions like Delhi, Maharashtra, and Kerala. Regional Virology Laboratory at AIIMS Bhopal completed sequencing of 44 Covid-19 positive samples collected between May and June 2025. The samples originated from Bhopal (14), Gwalior (22), Tikamgarh (2), and Indore, Khargon, Chhindwara, Lalitpur, Sidhi, and Gaya (one each). Analysis showed XFG variant as the dominant strain, present in 28 of 44 samples (63.6%). This variant, which developed from the LF.7 variant, was initially identified in May 2025, increased through early June, and became exclusive by late June. XFG.3, a new sub-variant evolved from XFG lineage, appeared in 5 of the 28 XFG-positive samples. The LF.7 variant, which represented 50% of samples in May, gradually decreased until its complete absence by late June. Both XFG and LF.7 variants can affect vaccinated individuals but have only caused mild or asymptomatic infections. The WHO has not categorised them as 'Variants of Concern' or 'Variants Under Monitoring.' AIIMS Bhopal director Dr Ajai Singh said, "AIIMS Bhopal Regional Virology Laboratory is working with scientific rigor to ensure that no emerging viral variant goes undetected. The early detection of variants like XFG and its sub-lineages helps us understand the virus's behavior and take timely precautionary public health measures." Regular genomic sequencing serves as an essential component of epidemic preparedness and response. AIIMS Bhopal advocates for consistent genomic surveillance of SARS-CoV-2 as a crucial public health activity in Madhya Pradesh and adjacent regions. This surveillance strategy enables early detection, prompt intervention, and improved readiness against potential future Covid-19 outbreaks or emerging variants.
Hans India
5 hours ago
- Hans India
Winter viruses can trigger heart attack or stroke; time for a Covid shot
Winter is almost here, along with cold days and the inevitable seasonal surge in respiratory viruses. But it's not only the sniffles we need to worry about. Heart attacks and strokes also tend to rise during the winter months. In new research out this week we show one reason why. Our study shows catching common respiratory viruses raises your short-term risk of a heart attack or stroke. In other words, common viruses, such as those that cause flu and Covid, can trigger them. Wait, viruses can trigger heart attacks? Traditional risk factors such as smoking, high cholesterol, high blood pressure, diabetes, obesity and lack of exercise are the main reasons for heart attacks and strokes. And rates of heart attacks and strokes can rise in winter for several reasons. Factors such as low temperature, less physical activity, more time spent indoors – perhaps with indoor air pollutants – can affect blood clotting and worsen the effects of traditional risk factors. But our new findings build on those from other researchers to show how respiratory viruses can also be a trigger. The theory is respiratory virus infections set off a heart attack or stroke, rather than directly cause them. If traditional risk factors are like dousing a house in petrol, the viral infection is like the matchstick that ignites the flame. For healthy, young people, a newer, well-kept house is unlikely to spontaneously combust. But an older or even abandoned house with faulty electric wiring needs just a spark to lead to a blaze. People who are particularly vulnerable to a heart attack or stroke triggered by a respiratory virus are those with more than one of those traditional risk factors, especially older people. Our findings: Our team conducted a meta-analysis (a study of existing studies) to see which respiratory viruses play a role in triggering heart attacks and strokes, and the strength of the link. This meant studying more than 11,000 scientific papers, spanning 40 years of research. Overall, the influenza virus and SARS-CoV-2 (the virus that causes COVID) were the main triggers. If you catch the flu, we found the risk of a heart attack goes up almost 5.4 times and a stroke by 4.7 times compared with not being infected. The danger zone is short – within the first few days or weeks – and tapers off with time after being infected. Catching Covid can also trigger heart attacks and strokes, but there haven't been enough studies to say exactly what the increased risk is. We also found an increased risk of heart attacks or strokes with other viruses, including respiratory syncytial virus (RSV), enterovirus and cytomegalovirus. But the links are not as strong, probably because these viruses are less commonly detected or tested for. What's going on? Over a person's lifetime, our bodies wear and tear and the inside wall of our blood vessels becomes rough. Fatty build-ups (plaques) stick easily to these rough areas, inevitably accumulating and causing tight spaces. Generally, blood can still pass through, and these build-ups don't cause issues. Think of this as dousing the house in petrol, but it's not yet alright. So how does a viral infection act like a matchstick to ignite the flame? Through a cascading process of inflammation. High levels of inflammation that follow a viral infection can crack open a plaque. The body activates blood clotting to fix the crack but this clot could inadvertently block a blood vessel completely, causing a heart attack or stroke. Some studies have found fragments of the COVID virus inside the blood clots that cause heart attacks – further evidence to back our findings. We don't know whether younger, healthier people are also at increased risk of a heart attack or stroke after infection with a respiratory virus. That's because people in the studies we analysed were almost always older adults with at least one of those traditional risk factors, so were already vulnerable. The bad news is we will all be vulnerable eventually, just by getting older. What can be done? The triggers we identified are mostly preventable by vaccination. There is good evidence from clinical trials that flu vaccines can reduce the risk of a heart attack or stroke, especially if someone already has heart problems. We aren't clear exactly how this works. But the theory is that avoiding common infections, or having less severe symptoms, reduces the chances of setting off the inflammatory chain reaction. Covid vaccination could also indirectly protect against heart attacks and strokes. But the evidence is still emerging. (Tu Nguyen is with the University of Melbourne. Co-writer Christopher Reid is from Curtin University, while Diana Vlasenko, Hazel Clothier and Jim Buttery are from Murdoch Children's Research Institute)
