* Nikkei down 2.4 pct, hit lowest since May 1 at one point * Exporters hit as yen strengthens, Panasonic tumbles * Flu-related stocks gain as worry spreads TOKYO, May 18 (Reuters) - Japan's Nikkei stock average fell 2.4 percent on Monday and at one stage hit its lowest point since May 1, with exporters such as Sony Corp hurt as the yen strengthened against the dollar. Panasonic dropped 7.6 percent after it forecast a bigger-than-expected annual loss following a record quarter of red ink, battered by weak demand, price falls and restructuring costs. Chugai Pharmaceutical rose on hopes for strong sales of the Tamiflu flu drug after the number of HIN1 flu cases climbed among Japanese who had not been abroad. But market analysts said worries about the impact of the virus on Japan's economy also gave investors an excuse to take profits. Currency moves were by far the biggest factor affecting the market, with the dollar sinking as low as 94.55 yen on electronic trading platform EBS as risk aversion grew after Wall Street closed weaker on Friday despite reassuring economic data. "Given that many exporters have set their currency rate at 95 yen, we're now getting to a worrisome level," said Takashi Ushio, head of the investment strategy division at Marusan Securities. Investors fret about a stronger yen as it eats into profits made abroad when repatriated. Companies such as Suzuki Motor Co, which has set its currency rate at 90 yen, fared better, rising 2.3 percent to 2,045 yen. Other analysts said the slide was mainly a reaction to Wall Street's Friday losses, noting that the Nikkei hit a six-month highs last week after gaining sharply and that a slight correction was not surprising. Moody's said it would hold a news conference at 3.00 p.m. (0600 GMT) about a new rating for Japanese government bonds after reviewing the latest financial conditions. No more details were immediately available. The benchmark Nikkei lost 221.45 points to 9,043.57 after falling as much as 2.9 percent to 8,997.74, its lowest since May 1. The broader Topix fell 2.3 percent 861.38. Analysts noted that the Nikkei's 25-day moving average now comes in at about 8,954 and could provide support, but that this would depend on whether the yen's advance against the dollar is halted. Among exporters, Canon Inc lost 5.4 percent to 3,130 yen, Kyocera Corp lost 1.9 percent to 7,360 yen and Sony tumbled 5.6 percent to 2,430 yen. Toyota Motor Corp fell 2 percent to 3,520 yen and Honda Motor Co shed 3.1 percent to 2,680 yen. Chugai, which distributes Tamiflu through its partnership with developer Roche, bucked the trend to rise 4.2 percent to 1,842 yen, becoming the biggest contributor to the Nikkei 225 by volume weight. Shares of companies that make medical masks and fabrics used for them also jumped. Unitika Ltd surged 21.7 percent to 112 yen and Fujibo Holdings Inc soared 30.3 percent to 129 yen, up by its daily limit Shikibo and Daiwabo Co Ltd were untraded due to a glut of buy orders, with both stocks bid up by their daily limit. Shares of Autobacs Seven Co Ltd jumped 7.1 percent to 3,150 yen after the auto parts retailer forecast a 77 percent rise in operating profit for the year to March 2010 and announced it would buy back and cancel its own shares.

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