David Schneider from Stanford University has suggested an interesting way to look at the delicate relationship (Diagram below) between infection and the degree of health last week in Chicago.
During an usual infection (blue line), whether it is bacteria or virus, when the infection load increases (1), your health status gets worse. At some point, your immune system gets fully activated (2) and begins to fight off the infection (3). When you are recovered from the infection, you are at point 4 on the diagram.
For some unlucky patients, their immune system may be dysfunctioned, due to genetic predisposition or chemotherapy or etc. They can end up as represented by the red line that shows an increase and uncontrolled infection load, which results in death at the end.
For immune dysfunctioned individuals with bloodstream infection of staph aureus (such as people with HIV, or who recently gone through chemotherapy or who with a certain tissue malignancy), the mortality can be found concentrated between 30 to 90 days after first getting hospitalized. Thus, it suggests that the immune defense against the first pathogen assault was not compromised, but the defense is not capable to control and prevent the “re-growth” of the pathogen.
This diagram above nicely lays out the proposed infectious cycle of staph aureus infection in bloodstream in immune dysfunctioned patients. At stage 1, the immune system is activated. At stage 2, the immune system is activated and begins to control and fight off the infection. At stage 3, the immune system somehow shuts down or unable to continue, and the bacteria begins to increase. At stage 4 and beyond, the bacteria load continues to increase, which results in death.
The conventional way to look at this relationship is to plot infection load against time. This new model enables us to ask questions, such as “does a prior infection of pathogen a give me a heightened health status after recovery?”, and “How do we access the status of health in a clinical setting?”.