however, according to chessgames:

Harry Nelson Pillsbury beat Wilhelm Steinitz 6 to 5, with 3 draws>

<percyblakeney: Pillsbury did win their last decisive games, but by then Steinitz was far from healthy>

At London, 1899, Steinitz did not play well and for the first time in his career he did not finish among the leaders and did not receive a prize. He played poorly against several players, including Pillsbury. It seems most likely that Steinitz was not well during this tournament.

Pillsbury also suffered from illness during his playing career. His ill health was caused by syphilis, which caused his death at age 33, and affected his results from St. Perersburg 1895/96 on until the end of his short playing career.

At Vienna 1898, Steinitz actually played very well. Of course, he was past his peak, but there was no evidence of his being not well. He finished a strong 4th, a full 2 points ahead of the 5th place finisher Schlechter, and 3 1/2 points ahead the the 6th and 7th place finishers Burn and Chigorin.

Steinitz played his last game in the Vienna tournament on July 25th. On August 2nd, 1898, the 11th German Chess Association Congress began at Cologne. At Cologne, Steinitz finished a clear 5th in a field of 16, 1/2 point ahead of Schlechter and Showalter. Burn won this tournament, 1 point ahead of Charousek, Chigorin & Cohn and 2 points ahead of Steinitz. Burn considered his win over Steinitz at Cologne, 1898, to be the best tournament game he ever played.

7 players played at both Vienna and Cologne 1898. Here are their combined scores for these tournaments.

Janowski & Steinitz - 34 points
Burn - 32.5 points
Chigorin & Schlechter - 31.5 points
Schiffers & Showalter - 25 points

Steinitz's 24.5 total at Vienna almost matched Schiffers's and Showalter's total for both tournaments. Certainly, Steinitz played very well in both of these tournaments.