Editing Openai/680845c9-c944-8012-bafb-fa1bab1e9277 (section)

==== We'll use a representative example: Measles virus (MeV). Later, we can examine others (e.g., SARS-CoV-2, Influenza, Polio, HIV). ====

Let’s break it down:

===== - Clusters of patients, often children, exhibit similar symptoms (rash, fever, respiratory illness). =====
* Epidemiological tracking identifies patterns of spread and incubation.
* These illnesses are contagious and predictable.

✅ Step satisfied.

===== - A common infectious agent — likely a virus — causes these symptoms. =====
* The hypothesis: A virus replicates in the body, is transmitted via droplets, and causes disease.

✅ Step satisfied.

===== - If the hypothesis is correct: - We should find viral material (RNA/proteins) in patients - The virus should replicate in human or primate cells - It should provoke an immune response - Animals exposed to the virus should develop disease (under ethical conditions) =====

✅ Step satisfied.

===== This is where much of the confusion arises, so let’s clarify: =====
* Virus isolation from patients is achieved through filtration, centrifugation, and microfluidic sorting.
* Sequencing confirms the genome.
* Animal studies in non-human primates (e.g., cynomolgus macaques) show that the virus replicates and causes measles-like illness.
* Antibodies from exposed individuals neutralize the virus.
* Vaccines made from live-attenuated virus prevent disease — a result that only makes sense if the virus is real and causative.

✅ Step satisfied (with indirect human data, plus direct animal models).

===== - Independent labs around the world isolate the measles virus, sequence it, grow it in Vero cells, produce vaccines, and detect it via PCR and ELISA. =====
* Decades of data confirm its genetic stability, modes of transmission, and immune response.

✅ Step satisfied.

===== - Thousands of peer-reviewed publications, regulatory agency documents (CDC, WHO, EMA), and vaccine trials have confirmed measles virus properties and disease causality. =====

✅ Step satisfied.