The infection hypothesis proposes that the development of chronic inflammation and lipid accumulation presented by atherosclerosis occurs via complex pathways in response to injury. Several seroepidemiological studies have demonstrated respiratory, periodontal, and gastric (H. pylori) infectious pathogens in the implication of atherosclerosis. Direct mechanisms include acceleration of lesions and vascular infection, while indirect mechanisms occur via cytokine production and acute phase proteins.

Current studies have shown the role of particular viral pathogens as well as atypical fungi in the pathogenesis and the exacerbation of chronic asthma. A study by Hahn et al. and another by Kraft et al. demonstrated that patients with C. pneumoniae infection progressed to chronic asthma and patients with asthma that tested positive for M. pneumoniae or C. pneumoniae showed improvement in lung function following treatment.

Depression is the most common mental disorder and affects 1 in 4 individuals. The various causes of depression are poorly understood but research suggests that specific viral and bacterial pathogens may play a role in the onset of Major Depressive Disorder (MDD) following the body’s immune response to external stress, post infection.

There is no known cause or cure for encephalomyelitis/chronic fatigue syndrome (ME/CFS). Some possible links to causes include chronic production of cytokines, low-functioning natural killer (NK) cells, and differences in markers of T-cell activation (chronic immune stress), chronic physical or emotional stress, changes in energy production, and genetics. Several pathogens have been linked to ME/CFS in severe cases of infection, such as, EBV, human herpesvirus 6, mycoplasma, and C.albicans.

Prostatitis, inflammation of the prostate gland, is caused by various factors including infection. Prostatitis is the most common prostate problem in men under the age of 50 and almost 50% of adult men experience symptoms. Some atypical pathogens which have been found in cases of bacterial prostatitis are C. trachomatis, T. vaginals, and U. urealyticum.

Rheumatoid Arthritis (RA) is a common and complex autoimmune disease. Clinical studies involving animal models have shown that microbial infections may cause or worsen symptoms of this disease. C. thrachomatis has been seen to cause oligoarticular or polyarticular sterile arthritis, while viruses like HIV, parvovirus, as well as hepatitis B and C, may cause acute or chronic forms of arthritis.

A Sexually Transmitted Disease (STD) is a disease that is normally passed from one person to another through sexual activity. According to the World Health Organization, more than 1 million STIs are reported every day. STIs may display immediate symptoms but they may also increase one’s risk of contracting HIV (herpesvirus and syphilis), cause neonatal complications, lead to cervical cancer (HPV) or Pelvic Inflammatory Disease (PID-gonorrhoea and chlamydia).

Tick-borne pathogens are responsible for 95% of vector borne disease in the US, with Lyme disease being the most prevalent. Tick species like the Ixodes scapularis (blacklegged deer tick) and Amblyomma americanum (lone star/ cricker/ turker/ northeastern water tick) are becoming more widespread, causing an increase in tick disease cases.

R702W, G908R, and 1007fs mutations have been previously found on Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) (a.k.a. caspase recruitment domain-containing protein 15 gene (CARD15)) in patients with CD and ulcerative colitis (UC).In a meta-analysis, it was found that the risk for developing CD increased 2.4 fold for carriers of a single mutation and 17.1 fold in affected or compound heterozygotes.

Conjunctivitis can cause allergic reaction and eye irritation. Risk factors are: exposure to someone virally infected, using contact lenses.

Dental bacterial infections can cause dental carries, periodontitis, etc. Risk factors are: poor habits and care, dry mouth, high sugar diet, etc.