The former Wimbledon champion Marion Bartoli has hit back at internet trolls who have targeted her over her dramatic weight loss, saying she fears for her life after contracting a mystery virus.

Bartoli, 31, has been the victim of online abuse and suggestions that she has an eating disorder after losing up to 5st (30kg) since she won the tournament in 2013.

However, in an interview with ITV’s This Morning on Thursday, the Frenchwoman said doctors had diagnosed her with a virus they were unable to identify. It has left her unable to eat anything other than organic salad leaves and made her hypersensitive to tap water and electrical devices.

“It’s absolutely horrendous,” she said. “My life right now is an absolute nightmare. What I am going through, I wouldn’t wish it on [anyone].

“I can’t even wash myself with tap water ... I can’t be on my phone for more than five minutes as my heart starts to pump ... Every time I do something, I’m scared to see the reaction to my body, it’s a constant fear.

“I’m reduced to eating organic salad leaves with cucumber without the skin, because my body can’t even process the skin.” She said she would begin treatment for the condition on Monday.

Asked if she feared death, she said: “Yes, of course, because maybe one day my heart is going to stop ... but my passion and love for life is keeping me going.”

Refuting suggestions she has an eating disorder, Bartoli said: “I love to eat and drink, I love life and I want to be alive.”

She said she had chosen to speak out because of the many negative tweets she had received. “That’s why I wanted to come here and explain to them. Maybe there are other people around the world suffering the same, and maybe we can all join and be supportive.”

Marion Bartoli on the way to winning the Wimbledon ladies singles title in 2013. Photograph: Tom Jenkins/The Guardian

Bartoli found herself at the centre of a sexism storm when she won Wimbledon. BBC commentator John Inverdale suggested she had dedicated herself to tennis because she was “never going to be a looker”. Inverdale later apologised for his “ham-fisted” comments.

Bartoli, now a commentator, had been due to play an invitation doubles match at Wimbledon this week. However, tournament officials replaced her over concerns about her health.

She said she had initially put her weight loss down to “going back to a healthy lifestyle” after retiring from tennis, but that her health had deteriorated in recent months.

Bartoli believes she contracted the virus in India. “I started to feel worse and worse. As the weeks were passing … my body was refusing more and more things.

“I hope and pray the doctors will be able to treat me … As a Wimbledon champion, I’m trying to fight my hardest to survive. I want people to understand that I don’t do [this] to myself on purpose; this is what I’m going through and it’s absolutely horrendous.”

Serena Williams, who will defend her Wimbledon title in Saturday’s ladies’ final, paid tribute to Bartoli for speaking out about her illness.

“I was really proud to hear she did say something,” said Williams. “She took it upon herself to acknowledge what she’s been fighting through. I really admire anyone that is courageous like that.”