Polish Nobel Peace laureate and communist-era opposition icon Lech Walesa will stay in hospital until at least next week due to gastric problems and a fever, he told AFP on Friday. \"I\'m feeling a bit better, but my fever has come back. My doctors still don\'t know the cause of my infection,\" Walesa said in a telephone interview from the University Clinical Centre in Gdansk, northern Poland. \"I don\'t know when I\'ll be able to leave hospital. I\'d like it to be at the start of next week, but the doctors want to keep me in for tests,\" he added. The clinic\'s deputy director, Tadeusz Jedrzejczyk, said he could not comment on 67-year-old Walesa\'s condition. \"We simply don\'t know,\" he was quoted as saying by Poland\'s news agency PAP. \"And as long as we only have hypotheses, we can\'t say anything.\" Jedrzejczyk underlined that there was no suspicion that frequent traveller Walesa was a victim of the enterohaemorrhagic E. coli poisoning which has hit more than 2,800 in at least 14 countries and claimed some 30 lives, mostly in Germany. Walesa decided to go for treatment on Wednesday -- at his wife\'s insistence, he said -- after feeling unwell the previous day. He has not let his spell in hospital get in the way of his avid blogging, and has been posting pictures from his stay at his site, lechwalesa.blip.pl. Walesa has diabetes and cardiac problems, and in 2008 was fitted with a pacemaker in a US clinic. As a shipyard electrician he was leader of Solidarity, a union born during a 1980 strike in the Baltic port of Gdansk that won grudging recognition from Poland\'s communist authorities. The government backtracked in 1981 and imposed martial law to crush Solidarity, but it kept alive underground. Walesa won the Nobel Peace Prize in 1983. Solidarity returned to the fore in 1989, negotiating an election deal with the regime and scoring a victory that helped bring down the entire Iron Curtain by 1991. In 1990, Walesa became Poland\'s first democratically-elected president since World War II, serving one five-year term. He has remained a respected democracy activist, and recently travelled to Tunisia to offer know-how for its transition.