"I didn't know too much about it at the time, how serious it could be, but I remember feeling very, very ill," Leach told the Daily Mail.
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"I remember thinking 'don't fall asleep because you might not wake up.' It was that serious in terms of how I was feeling. I was out of it really. My blood pressure was dropping quickly, my heart-rate was 190 and my temperature was 40 degrees. That's when they called an ambulance and got me to hospital.
"Once I got there, got the antibiotics in my arm and on to a drip, I started to feel better quite quickly but it still took a couple of nights in hospital and I was probably still recovering when I flew back from New Zealand. It took longer to get over than I thought."
Leach played in England's first test defeat in Mount Maunganui, taking two wickets in the match, which was his last international appearance for England.