Coronavirus - Park's Textbook of Preventive and Social Medicine

PART 1: SEVERE ACUTE RESPIRATORY SYNDROME (SARS)

Definition & Causative Agent

Clinical Features

• Fever, malaise, chills, headache, myalgia, dizziness, cough, sore throat, running nose
• Rapid deterioration with low oxygen saturation and acute respiratory distress in severe cases
• Case fatality: up to 10%
• Chest X-ray: begins as small unilateral patchy shadowing, progresses to bilateral generalized interstitial/confluent infiltration within 1-2 days
• ARDS in ~16% of patients; 20-30% require intubation and mechanical ventilation

Epidemiology

• First traced to a health care worker in China, late 2002; spread to Hong Kong, Singapore, Vietnam, Taiwan, and Toronto
• By August 2003: 8,422 cases from 30 countries; 916 fatalities
• Health care workers accounted for 21% of all cases
• Children rarely affected; no confirmed child-to-child transmission

Incubation Period

Mode of Transmission

• Primary: direct/indirect contact of mucous membranes (eyes, nose, mouth) with respiratory droplets or fomites
• Aerosol-generating procedures (intubation, bronchoscopy, nebulization) amplify transmission
• Virus shed in stools; fecal-oral role uncertain
• Natural reservoir: horseshoe bat (civets = amplifying host)
• Virus survives: hours on surfaces, up to 4 days in human waste, 24 hours on plastic at room temperature

Case Definition

• Suspected case: fever >38°C + lower respiratory symptoms + epidemiological link within 10 days
• Probable case: Suspected case with chest X-ray findings of pneumonia or ARDS, or autopsy findings consistent with pneumonia/ARDS without identifiable cause
• Laboratory-confirmed case: PCR, virus culture, or 4-fold antibody rise (ELISA/IFA) against SARS-CoV

Complications

• ARDS (~16%), intubation required in 20-30%
• Nosocomial infections, tension pneumothorax, non-cardiogenic pulmonary edema

Treatment

• Agents used (efficacy inconclusive): ribavirin, lopinavir/ritonavir, interferon type 1, IV immunoglobulin, systemic corticosteroids

Prevention & Control

• Isolation of cases within 5 days of onset significantly reduces secondary transmission
• Standard + contact + airborne precautions for healthcare workers
• Exit screening at airports during epidemic; WHO must be notified of every case

PART 2: CORONAVIRUS DISEASE-19 (COVID-19)

Definition & Causative Agent

• Single-stranded RNA virus (~60-140 nm diameter)
• Crown-like appearance with club/petal-shaped spikes under electron microscope
• Sensitive to UV rays, 75% ethanol, chlorine-based disinfectants, peroxyacetic acid, chloroform
• Resistant to cold temperatures; chlorhexidine is NOT effective

Global Scenario

• Spread to >200 countries; declared a pandemic by WHO on 11 March 2020
• UK variant (SARS-CoV-2 VOC 2020 12/01) reported December 14, 2020 - ~70% more transmissible
• South African variant (501Y.V2) reported December 18, 2020
• As of February 2021: ~110.8 million cases globally; ~2.45 million deaths; recovery rate 77.4%

Clinical Features

• Common symptoms: dry cough, fever, fatigue, loss of taste/smell
• Less common: body aches, sore throat, diarrhea, headache, rash
• Serious: difficulty breathing, chest pain, loss of speech/movement

Mode of Transmission

• Primarily via respiratory droplets and contact (touching contaminated surfaces, then touching mouth/nose/eyes)
• Airborne transmission possible in poorly ventilated spaces
• Fecal-oral route under investigation
• High-risk contact: within 3 ft of a confirmed case; touching body fluids; sharing household; travelling together >6 hours
• Basic Reproduction Number (R0): 2-2.5 (more contagious than SARS and MERS)

Incubation Period

High-Risk Groups

• Elderly, immunocompromised patients
• Comorbidities: cardiovascular disease, diabetes, chronic lung disease, hypertension, cancer
• Healthcare workers

Diagnosis

• Samples: nasopharyngeal + oropharyngeal swabs, bronchoalveolar lavage, tracheal aspirate, sputum
• RT-PCR targets: E gene (screening) and RdRp/N gene (confirmation)

• Point-of-care test; result in 15-30 minutes; sensitivity ~56-84%, specificity ~99%
• ICMR recommends use in high-prevalence settings

• IgM: appears at 5-7 days; IgG: appears at 14 days
• Not for acute diagnosis; used for seroprevalence studies

• Ground-glass opacities (GGO) bilaterally; reverse halo sign; crazy-paving pattern

Management (Indian Protocol)

• Paracetamol for fever/pain
• Steam inhalation, warm saline gargles
• Vitamin C, zinc supplementation
• Monitor SpO2 daily; seek care if <94%

• Injection methylprednisolone 0.5-1 mg/kg/day OR dexamethasone 0.1-0.2 mg/kg/day x 5-10 days
• Supplemental oxygen to maintain SpO2 >94%
• LMWH prophylaxis for thrombosis
• Remdesivir: 200 mg IV Day 1 then 100 mg IV daily x 4 days (total 5 days)

• Prone positioning, mechanical ventilation (lung-protective: tidal volume 4-8 mL/kg, PEEP-guided)
• Dexamethasone 0.2 mg/kg/day x 10 days
• Tocilizumab 8 mg/kg (max 800 mg) for progressive oxygen requirements with raised inflammatory markers
• Convalescent plasma (200 mL) in moderate-severe cases
• Thromboprophylaxis: therapeutic anticoagulation in suspected/confirmed VTE

Vaccines (as covered in Park's)

• Persons NOT eligible temporarily: recent COVID-19 infection, previous severe allergic reaction to vaccine, pregnancy (Covishield)

Prevention and Public Health Measures

• Hand hygiene: Wash hands frequently with soap/water (20 seconds) or use alcohol-based sanitizer
• Mask use: Surgical/N95 for healthcare workers; cloth/surgical mask for general public
• Physical distancing: Maintain at least 1-2 meters
• Quarantine: 14 days for contacts; home isolation for confirmed mild cases
• Lockdown, border closure, contact tracing, testing
• Aarogya Setu App (India): digital contact tracing app to identify individuals at risk

Surveillance

• COVID-19 included as a mandatory notifiable disease
• Two types of testing: (1) Diagnostic - for symptomatic/exposed individuals; (2) Screening - for asymptomatic persons
• Surveillance objectives: monitor trends, mortality in healthcare workers, impact of control measures
• Weekly aggregate reporting to WHO: confirmed cases, probable cases, confirmed deaths, healthcare worker infections