Coronavirus Outbreaks: SARS-CoV and MERS-CoV

• Coronaviruses are enveloped, positive-sense, single-stranded RNA viruses first discovered in the 1930s in domestic poultry.
• These viruses caused respiratory, gastrointestinal, liver, and neurologic diseases in poultry
• Seven coronaviruses are known to cause disease in humans.

Severe Coronavirus Outbreaks

• Three human coronaviruses have caused severe respiratory infections: SARS-CoV, MERS-CoV, and SARS-CoV-2.

SARS-CoV (2002 Outbreak)

• SARS-CoV caused the SARS outbreak in 2002, leading to severe respiratory insufficiency.
• The outbreak was first reported in Guangdong province, China.
• The virus likely originated in bats and then spread to civets before infecting humans.
• SARS spread to over 30 countries, affecting over 8,000 people and causing 774 deaths.
• Human transmission and widespread travel contributed to the rapid spread of SARS.

MERS-CoV (2012 Outbreak)

• MERS-CoV caused the MERS outbreak in 2012, resulting in severe acute respiratory illness.
• The first case was reported in Saudi Arabia, with a retrospective case identified in Georgia.
• The virus likely originated in bats and spread to dromedary camels, which became a reservoir for human infection.
• Person-to-person transmission helped spread MERS to 27 countries, affecting nearly 2,500 people and causing at least 850 deaths.
• All MERS cases were linked to living in or traveling to the Arabian Peninsula or close contact with infected individuals.

SARS-CoV-2 (COVID-19 Pandemic, 2019–Present)

• SARS-CoV-2 caused the COVID-19 pandemic, leading to acute and sometimes severe respiratory illness.
• The first cases were reported in Wuhan, China, and likely originated from live animal markets.
• The natural reservoir of the virus is still under investigation.
• COVID-19 spreads faster than the flu due to pre-symptomatic transmission and respiratory droplets landing on the T-zone (mouth, nose, eyes).
• Airborne droplets can remain infectious for up to 3 hours, and indirect transmission can occur via contaminated surfaces.
• A reproductive number (R₀) of 1 means each infected person spreads the disease to one new person.
• The R₀ of COVID-19 is 2–2.5, indicating it spreads more easily than seasonal flu (R₀ ~1.3).
• Elderly individuals and those with hypertension, diabetes, cardiovascular disease, chronic respiratory disease, or cancer are at higher risk.
• Children under nine years old rarely experience severe illness but can still spread the virus.

Diagnosis of COVID-19

• RT-PCR is used to detect small amounts of viral RNA in patient samples.
• Chest CT scans identify viral pneumonia in severe cases.
• Isothermal amplification is a rapid testing method that quickly detects viral RNA.
• Serological testing detects antibodies, useful for identifying past infections.
• Respiratory viral panels help rule out other respiratory infections.

Treatment of COVID-19

• Mild cases: Patients should isolate at home, rest, and stay hydrated.
• Severe cases: Treatment focuses on supportive care, including fluids, oxygen therapy, and ventilatory support.
• Remdesivir is an antiviral drug that some early studies showed a shortened duration of symptoms, but a randomized trial found no significant benefit over placebo.
• Other experimental drugs include Lopinavir/Ritonavir (HIV antiviral drugs), Chloroquine/Hydroxychloroquine (malaria drugs), and Azithromycin (antibiotic).

COVID-19 Symptoms and Complications

• Mild symptoms (80% of cases) include fever, cough, shortness of breath, fatigue, and loss of smell and taste.
• Severe symptoms include pneumonia, acute respiratory distress syndrome (ARDS), and septic shock.
• Complications include Pediatric Inflammatory Multisystem Syndrome (PIMS) in children, increased stroke risk in young adults, and pulmonary fibrosis.
• PIMS affects the heart-supplying blood vessels in children.
• Increased stroke risk in young adults is due to inflammation of large blood vessels.
• Pulmonary fibrosis is a chronic lung disease that can affect even young and healthy individuals.