The makers of the multiple sclerosis drug Tysabri said yesterday that a second patient who used the drug had been confirmed to be suffering from a rare but deadly brain infection. The confirmed diagnosis is likely to somewhat diminish the chances that the drug will be able to return to the market. The makers of the drug, Biogen Idec and Elan, halted sales and clinical trials on Monday, saying that one patient in a clinical trial had died from the brain infection and a second patient from the same trial, who was still alive, was also suspected of having it....