Viruses and viral disease

This branch covers viruses and the diseases they cause, and its parts divide by what a question is about: what any virus is and how it spreads, a particular virus or family of viruses and the disease it causes, or the drugs that act against a virus. It leaves vaccines to the branch on vaccines, and the airway in health to the respiratory system.

• What a virus is and how it spreads — what a virus is, how abundant viruses are and what else they do, their size, genome and particle, classification and naming, how a virus enters, replicates in and leaves a cell, virulence, immunity, mutation and emerging viruses, types and strains, what a pandemic is and why pandemics recur, the basic reproduction number, and quarantine, isolation and contact tracing
• Coronaviruses: SARS, MERS and SARS-CoV-2 — the family and its structure, the SARS and MERS outbreaks, where SARS-CoV-2 came from and why the outbreaks come from bats, how it spreads and how its spread is stopped, and who fell ill and what was still unknown in May 2020
• SARS-CoV-2 and influenza in the respiratory tract — the two viruses and their surface proteins, how each enters and leaves a cell, where in the airway each takes hold, how infection and the defence against it produce the symptoms, why ARDS starves the blood of oxygen and how mechanical ventilation helps, how many each virus infects and kills, and how the two spread
• COVID-19 and the cardiovascular system — how firm the evidence was in mid-2021, how SARS-CoV-2 harms the heart and vessels, the conditions that follow, why preexisting heart disease matters, and what was known in mid-2021 about blood-pressure medicines and about COVID-19 treatments with cardiac risks
• Zika and chikungunya — two viruses carried by Aedes mosquitoes: how Zika spreads, Zika infection and congenital Zika syndrome, preventing Zika, chikungunya and its symptoms, and where chikungunya occurs, including its sporadic transmission in Europe
• Antiviral drugs — why so few antiviral drugs exist, the steps of the coronavirus life cycle the most promising drugs of May 2020 acted at, and ribosomal frameshifting, a step not then investigated as a drug target