This is an observational prospective study of an in-vitro diagnostic (IVD) assay planned to enroll 632 subjects. The study will be conducted in two stages: Stage A is aimed at identifying individual biomarkers and constructing a multi-parametric diagnostic model, whereas Stage B is aimed at testing the multi-parametric diagnostic model using a fresh cohort of patients.

A collection of clinical, radiological and laboratory data will be gathered in order to establish a final diagnosis. Blood samples will be analyzed and the levels of approximately 700 and 250,000 biomarkers will be determined using immunoassays and molecular measurements respectively.

A final diagnosis will be determined based on a majority decision of a panel of three or more independent physicians. Based on the final diagnosis, the accuracy of individual biomarkers and combined sets of biomarkers for differentiating between distinct groups of patients will be evaluated.

Inclusion Criteria:

Patients who are at least one month old and are willing (either the subject or his legal guardian) to sign an informed consent will be eligible for inclusion. For the infectious and non-infectious disease groups, additional inclusion criteria have to be met. These will include:

In the Infectious disease group:

• Peak fever >37.5°C (99.5°F)
• Clinical suspicion of an acute infectious disease
• Symptoms duration ≤ 12 days

In the Non-infectious disease control group:

- A non-infectious disease or healthy individuals

Exclusion Criteria:

Patients who will meet one or more of the following criteria will be excluded from the study:

• Evidence of another episode of acute infectious disease in the last two weeks
• Diagnosed congenital immune deficiency (CID)
• Current treatment with immunosuppressive therapy such as: Active chemotherapy,Post-transplant drugs,High dose steroids (>1 mg/kg/day prednisone or equivalent).
• Active radiotherapy
• Immune-modulating/suppressive drugs including monoclonal antibodies, intravenous immunoglobulin (IVIG), cyclosporine, and anti-TNF agents
• Current treatment with immune stimulants such as: Interleukin (IL)-2, Granulocyte-Monocytes/Granulocyte colony-stimulating factor (GM/G-CSF),Interferon.
• An active hematological malignancy
• A diagnosis of myelodysplastic syndrome or myeloproliferative disease
• A proven or suspected human immunodeficiency virus (HIV)-1, hepatitis B virus (HBV), or hepatitis C virus (HCV) infection

Eligible subjects aged one month of age and older from both genders that attend the hospital or the emergency room (ER) due to a suspected acute infectious disease or due to a non-infectious disease (e.g. Trauma).