Rebecca Adlington has spoken of the trauma of seeing her older sister Laura in a coma after contracting encephalitis - and has said doctors don't yet know enough about the disease.
This comes as the debate about vaccinations against diseases such as measles encephalitis rages on in the US.
"Our mum and dad shielded me from the worst but it was obvious it was very serious," Adlington told the Express. "Laura had been taken into hospital with a crazy temperature but seemed to be improving. Then one day her eyes began rolling and she just said, 'call the nurse'.
"She was whisked away to intensive care and all sorts of possible causes, including meningitis, were investigated. I remember arriving at the hospital to find my parents crying.
"For a few days we didn't know what was wrong with Laura and, of course, we feared the worst."
10 Sports Stars Who Retired Too Young
10 Sports Stars Who Retired Too Young
1/10 Rebecca Adlington, Swimmer
Won: 2 Gold medals, 2 Bronze in the Beijing 2008 and London 2012 Olympics.
Retired: Aged 25.
2/10 Martina Hingis, Tennis Player
Won: 5 Grand Slam singles titles and 9 Grand Slam doubles titles.
Retired: Aged 22 the first time round, but she came out of retirement for a world tour in 2006 at 26, before withdrawing from the sport again.
3/10 Amy Williams, Skeleton
Won: 1 Gold medal at the 2010 Vancouver Olympics.
Retired: Aged 26 shortly after her win. She made her commentating debut during Sochi 2014.
4/10 Justine Henin-Hardenne, Tennis Player
Won: 43 WTA singles titles and 7 Grand Slam singles titles.
Retired: Aged 28, due to on-going injuries.
5/10 Rocky Marciano, Boxer
Won: 49-0 heavyweight wins, with 43 knock-out victories between 1948–1955.
Retired: Aged 32.
6/10 Bjorn Borg, Tennis Player
Won:16 Grand Slam singles titles, 101 career singles titles and five consecutive ATP Player of the Year titles between 1976-1980 .
Retired: Aged 26.
7/10 Mark Spitz, Swimmer
Won: 9 Olympic golds, one silver and one bronze.
Retired: Aged 22.
8/10 Elena Dementieva, Tennis Player
Won: 16 WTA singles titles and an Olympic gold medal.
Retired: Aged 29.
9/10 Michael Jordan, basketball player
Won: 7 straight seasons as NBA's top scorer and 3 straight Finals MVP awards
Retired: Aged 30 the first time round, in 1993. Jordan came out of retirement briefly, only to retire again in 1998.
10/10 Kim Clijsters, tennis player
Won: 41 WTA singles titles and 11 WTA doubles titles
Retired: Aged 25
Encephalitis causes an inflammation of the brain and, while it is rare, it is serious. It begins with flu-like symptoms, fits and changes in personality and behaviour. Around 10 per cent of encephalitis cases are fatal, and the Encephalitis Society estimates that around 6,000 people in the UK are diagnosed with the disease every year.
Laura Adlington slowly recovered, but was put in a coma for four days while doctors struggled to work out the cause of her illness. She now suffers with migraines and short-term memory loss.
"So many families endure what we did 10 years ago yet relatively little is known about encephalitis," says Rebecca. "It's also important to fund research."
Adlington, who has won four Olympic medals for swimming, said that seeing her sister so unwell was a shock. "We did everything together and it was shocking when I was eventually allowed to see her in hospital with all the machines bleeping. None of us had heard of encephalitis."
She also added that swimming helped her emotionally recover from the trauma of seeing her sister so unwell. "Swimming was a great escape when Laura was very ill," she says. "It helped take my mind off what was happening. I was surrounded by people I knew and the pool became a safe place for me."
It is World Encephalitis Day on 22 February, and the Encephalitis Society is attempting to increase awareness of the disease and encourage doctors and the public to learn more about it.Reuse content