Please note the following caveats when considering this data: Invasive illness in this situation is defined as any report in which a sample from a normally sterile site has been taken for clinical diagnosis, as reported through ECOSS (sample sites considered: blood, cerebrospinal fluid, pleural and ascetic fluid, pleural and joint aspirate). The date the first sample was taken from an individual has been used as a proxy for date of onset of illness as detailed information on date of onset of illness is not available through ECOSS.