* anticipated transfer to another medical center that is not a study site within hours of admission to the icu. * pregnancy based on a positive human chorionic gonadotropin (hcg) test from serum or urine. * patient who is breastfeeding and unable to discontinue breastfeeding while taking the study drug. * patients with a diagnosis of invasive aspergillosis/detection of aspergillus spp. by culture from sputum, ta, ba, or balf or positive gm from serum or balf at time of screening or randomization. * history of invasive aspergillosis within the prior six months. * patients with a known intolerance or hypersensitivity to isavuconazole or other azole agents. * history of familial short qt syndrome. * patients that are being treated with mold-active antifungal agents for invasive aspergillosis or another invasive fungal infection. * patients with severe hepatic impairment or liver cirrhosis (child c) should be excluded from the study unless the treating physicians feel the benefits of treatment outweigh the risks. * treatment with lopinavir/ritonavir for hiv infection. * prohibited medications * co-administration with a strong cyp3a4 inhibitor or high-dose ritonavir as they may alter the plasma concentration of isavuconazole. * co-administration with a strong cyp3a4 inducer such as rifampin, carbamazepine, st. john's wort, or long acting barbiturates.

* anticipated transfer to another medical center that is not a study site within hours of admission to the icu. * pregnancy based on a positive human chorionic gonadotropin (hcg) test from serum or urine. * patient who is breastfeeding and unable to discontinue breastfeeding while taking the study drug. * patients with a diagnosis of invasive aspergillosis/detection of aspergillus spp. by culture from sputum, ta, ba, or balf or positive gm from serum or balf at time of screening or randomization. * history of invasive aspergillosis within the prior six months. * patients with a known intolerance or hypersensitivity to isavuconazole or other azole agents. * history of familial short qt syndrome. * patients that are being treated with mold-active antifungal agents for invasive aspergillosis or another invasive fungal infection. * patients with severe hepatic impairment or liver cirrhosis (child c) should be excluded from the study unless the treating physicians feel the benefits of treatment outweigh the risks. * treatment with lopinavir/ritonavir for hiv infection. * prohibited medications * co-administration with a strong cyp3a4 inhibitor or high-dose ritonavir as they may alter the plasma concentration of isavuconazole. * co-administration with a strong cyp3a4 inducer such as rifampin, carbamazepine, st. john's wort, or long acting barbiturates.

- anticipated transfer to another medical center that is not a study site within hours of admission to the icu. - pregnancy based on a positive human chorionic gonadotropin (hcg) test from serum or urine. - patient who is breastfeeding and unable to discontinue breastfeeding while taking the study drug. - patients with a diagnosis of invasive aspergillosis/detection of aspergillus spp. by culture from sputum, ta, ba, or balf or positive gm from serum or balf at time of screening or randomization. - history of invasive aspergillosis within the prior six months. - patients with a known intolerance or hypersensitivity to isavuconazole or other azole agents. - history of familial short qt syndrome. - patients that are being treated with mold-active antifungal agents for invasive aspergillosis or another invasive fungal infection. - patients with severe hepatic impairment or liver cirrhosis (child c) should be excluded from the study unless the treating physicians feel the benefits of treatment outweigh the risks. - treatment with lopinavir/ritonavir for hiv infection. - prohibited medications - co-administration with a strong cyp3a4 inhibitor or high-dose ritonavir as they may alter the plasma concentration of isavuconazole. - co-administration with a strong cyp3a4 inducer such as rifampin, carbamazepine, st. john's wort, or long acting barbiturates.

- anticipated transfer to another medical center that is not a study site within hours of admission to the icu. - pregnancy based on a positive human chorionic gonadotropin (hcg) test from serum or urine. - patient who is breastfeeding and unable to discontinue breastfeeding while taking the study drug. - patients with a diagnosis of invasive aspergillosis/detection of aspergillus spp. by culture from sputum, ta, ba, or balf or positive gm from serum or balf at time of screening or randomization. - history of invasive aspergillosis within the prior six months. - patients with a known intolerance or hypersensitivity to isavuconazole or other azole agents. - history of familial short qt syndrome. - patients that are being treated with mold-active antifungal agents for invasive aspergillosis or another invasive fungal infection. - patients with severe hepatic impairment or liver cirrhosis (child c) should be excluded from the study unless the treating physicians feel the benefits of treatment outweigh the risks. - treatment with lopinavir/ritonavir for hiv infection. - prohibited medications - co-administration with a strong cyp3a4 inhibitor or high-dose ritonavir as they may alter the plasma concentration of isavuconazole. - co-administration with a strong cyp3a4 inducer such as rifampin, carbamazepine, st. john's wort, or long acting barbiturates.