If you’ve suffered bouts of nausea, a fever and muscle aches, you could be forgiven for assuming your body was battling an infection. 

But experts have now warned that it may be a major warning sign that a rare, genetic heart condition may be about to strike.

Chest pains and and being short of breathe are well-known red flags of cardiac arrests — sudden loss of all heart activity, that often proves deadly.

Yet, according to Swedish researchers, palpitations, fainting, nausea and signs of an infection like muscle aches and fevers, are also common symptoms suffered by those with sudden arrhythmic death syndrome (SADS).

The condition — when someone dies from a cardiac arrest but no cause can be identified — affects around 500 people in the UK every year, according to the British Heart Foundation (BHF).

It comes after a string of incidents involving young and supposedly fit and healthy young people dramatically collapsing during sports matches or suffering fatal cardiac events. 

Last August, Poppy Eagle, from Washington, in Tyne and Wear, died after her heart stopped, despite no known history of health problems.

The 20-year-old fashion student had returned home from a dog walk ready for a movie night with her siblings when she suddenly collapsed. Her cause of death was later ruled to be SADS. 

Last August, Poppy Eagle (left), from Washington, in Tyne and Wear, died from SADS after her heart stopped, despite no known history of health problems

Natalie Black, a sophomore at Jackson’s Belhaven University, passed away while taking a nap

The promising athlete had accomplished her goal of beating her triple jump personal record just hours earlier – launching herself 11.01 meters and winning second place in the category

While some warning signs are easy to spot — such as severe chest pain — others are more vague and hard to pinpoint

Last month, promising athletics star Natalie Black, 19, passed away in her sleep just hours after competing in a college track and field event, beating her triple jump personal record. 

In the fresh study, researchers tracked 903 cases of sudden cardiac deaths in Sweden among people aged one to 36-years-old between 2000 and 2010. 

The researchers found that SADS accounted for 22 per cent of all sudden cardiac deaths. 

Almost two-thirds of SADS cases (64 per cent) were male, while the average age at death stood at just 23.

Around half (52 per cent) of all cases had experienced symptoms before their death, the scientists said.

The most common were ‘palpitations, fainting, nausea and vomiting and signs related to suffering from an infection’, they added. 

The findings, presented today at the European Society of Cardiology’s annual Preventive Cardiology conference in Milan, also showed that 4.2 per cent of all SADS fatalities had been hospitalised after fainting. 

Roughly one in 25 (3.5 per cent) had also previously been hospitalised after suffering convulsions. 

The research also comes just months after young and supposedly healthy footballers have collapsed mid-match on the pitch. Uruguayan footballer Juan Izquierdo, 27, collapsed in August last year tragically dying later in hospital 

Tom Lockyer (left months after the event) suffered a cardiac arrest during a Premier League game (right) which saw his heart stop for two-and-a-half minutes

A third of all SADS victims had visited hospital in the six months prior to their death.  

Dr Matilda Frisk Torell, an expert in cardiology at the University of Gothenburg and study author, said: ‘SADS has not been well evaluated despite being one of the most common underlying causes of sudden cardiac death in young people, including young athletes.

‘With increased knowledge of the signs and symptoms that may precede SADS, such as fainting, seizure-like episodes and pre-excitation, we may be able to identify young people at risk during healthcare visits. 

‘Our results also highlight the need for further study of psychiatric disease and treatment as risk factors for SADS and the potential for gastrointestinal symptoms and infectious diseases to act as triggers in predisposed individuals. 

‘Screening of young athletes is an important opportunity to identify these signs and reduce the occurrence of SADS, and yet current levels of screening are low.’ 

Families of the bereaved in Britain have long called for a nationwide screening programme to identify those at risk. 

Yet, the Government currently has no plans to implement one.  

The research also comes just months after a number of young and supposedly healthy footballers have collapsed mid-match on the pitch. 

Danish soccer player Christian Eriksen suffered a cardiac arrest at Euro 2020

Eriksen collapsed on the pitch in dramatic scenes in 2021. His collapse was later pinned on an undetected ventricular fibrillation, another condition that leads to heart rhythm disruption

Uruguayan footballer Juan Izquierdo, 27, collapsed in August last year tragically dying later in hospital. 

And Luton Town captain Tom Lockyer suffered an on-pitch heart attack last December with his heart stopping for two-and-a-half minutes.

All of this follows Danish footballer Christian Eriksen famous collapse during a Euro 2020 match.

Despite conspiracy claims to the contrary, experts have consistently told MailOnline these events, while tragic and rare, are not on the rise and recent clusters of cases are coincidental.

Izquierdo’s death was eventually revealed to be the result of a viral infection putting extra strain on his heart, causing it to beat in an irregular rhythm, medically called cardiac arrhythmia.

Lockyer’s collapse was linked to atrial fibrillation — a health condition that causes the heart to beat irregularly and abnormally faster and can trigger a heart attack.

Meanwhile Eriksen’s collapse was pinned on an undetected ventricular fibrillation, another condition that leads to heart rhythm disruption.

Renowned experts in cardiac health issues in young athletes have told MailOnline there has been no rise in deaths or in fact cases overall, in recent years.

NHS data shows a rise in the number of younger adults suffering from heart attacks over the past decade. The biggest increase (95 per cent) was recorded in the 25-29 year-old demographic, though as numbers of patients are low even small spikes can look dramatic 

But alarming data last year revealed that premature deaths from cardiovascular problems generally, such as heart attacks and strokes, had hit their highest level in more than a decade. 

MailOnline has previously highlighted how the number of young people, under 40, in England being treated for heart attacks by the NHS is on the rise. 

Cases of heart attacks, heart failure and strokes among the under-75s had tumbled since the 1960s thanks to plummeting smoking rates, advanced surgical techniques and breakthroughs such as stents and statins.

But now, rising obesity rates, and its catalogue of associated health problems such as high blood pressure and diabetes, are thought to be one of the major contributing factors. 

Slow ambulance response times for category 2 calls in England — which includes suspected heart attacks and strokes — as well as long waits for tests and treatment have also been blamed.