The 28-year-old batsman has successfully rebuilt his fitness during six months in New Zealand and will play in Sussex's opening Benson and Hedges Cup match against Gloucestershire at Bristol next week.
Speight lost over a stone in weight with the virus, which affects the muscles and joints, but said that his winter trip had gone so well that a specialist's check was not required.
"There were some dark days last season but after a full winter to test my fitness I feel fine and am ready to go," he said.
"After the effects of playing in just one second XI game last season I knew that I had to concentrate on getting completely right for this year, and it's worked out well.
"I felt fine during the whole of my time in New Zealand when I batted a lot for a side in the Wellington competition, kept wicket and also coached."
Speight is delighted to be making a comeback under the former West Indies captain Desmond Haynes, who has taken over as Sussex's new first-team coach. "Desmond has got everybody relaxed, he wants us to enjoy our cricket without feeling weighed down and the mood in the camp is excellent," he said.
Sussex have not won a trophy for nine years, but Speight says dwelling on their winless run only creates pressure. "I don't even think about it. Desmond believes success will come if we relax and play our natural game. He wants to bring on the best aspects of our cricket and I certainly won't be curbing my attacking instincts."
Haynes said: "A full season from Martin should make a big difference to our batting line-up, which was very inconsistent last year. I knew from my time at Middlesex that Martin was respected and bowlers such as Angus Fraser didn't always enjoy facing him, as on his day he can take any attack apart."
Lancashire are to give a first-class debut to South Africa's Steve Elworthy in the three-day friendly against Yorkshire at Old Trafford, which starts today. Elworthy, a 31-year-old all-rounder from Transvaal signed to replace Wasim Akram, is named in a 13-man squad.
Lancashire are without Mike Watkinson, Jason Gallian, John Crawley and Glen Chapple, who are all included in The Rest to play England A at Chelmsford on Saturday.
Mike Atherton will captain the side in the absence of Watkinson while the youngsters Andrew Flintoff, Richard Green and Darren Shadford are in contention for a place.
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