Respiratory

Acute Respiratory Infection — Upper & Lower

Q: When do you need antibiotics for sore throat?

Only for Group A Streptococcal pharyngitis, which causes 20% of adult pharyngitis. Use Centor criteria: fever, tonsillar exudate, tender anterior cervical lymphadenopathy, absence of cough — score 3-4 suggests strep, treat with Penicillin V 500 mg BD x 10 days OR single dose Benzathine Penicillin 12 lakh units IM. Avoid azithromycin — high resistance. Viral pharyngitis (80%) — symptomatic treatment only.

Q: What is the difference between acute bronchitis and pneumonia?

Acute bronchitis is inflammation of bronchi, usually viral, presents with cough > 5 days ± sputum, normal chest X-ray. Self-limiting, no antibiotics. Pneumonia is infection of lung parenchyma (alveoli), presents with fever, cough, dyspnoea, chest pain, focal crackles on auscultation, infiltrate on chest X-ray. Requires antibiotics — outpatient (oral Amoxicillin or Doxycycline) or inpatient (IV Ceftriaxone ± Azithromycin) based on severity.

Q: What is the Centor criteria for strep throat?

4 criteria — Fever, Exudate on tonsils, tender anterior cervical Lymphadenopathy, absence of Cough. Score 0-1: no testing, no antibiotics. Score 2: rapid strep test or throat culture. Score 3-4: empiric antibiotics (Penicillin V or Amoxicillin). Avoid macrolides (azithromycin) for strep throat due to high resistance rates in India.

Q: How do you prevent acute respiratory infections?

Hand hygiene (soap and water or alcohol-based), avoid close contact with sick people, wear mask in crowded settings during flu season, annual influenza vaccine for high-risk groups (elderly, healthcare workers, pregnant women, chronic disease), pneumococcal vaccine (PCV13 + PPSV23) for elderly and immunocompromised, COVID-19 vaccination, smoking cessation, reduce indoor air pollution (LPG, ventilation).

By Dr. Sonu Lakeshar

Acute Respiratory Infection (ARI) is the most common reason patients visit a doctor in India. It ranges from trivial common cold to life-threatening pneumonia. Distinguishing viral from bacterial, upper from lower, and self-limiting from serious is the everyday clinical skill every MBBS doctor must master. ARI is also among the top 5 causes of antibiotic misuse.

On This Page

Overview
Upper ARI
Lower ARI
Antibiotic Stewardship
FAQs

Overview

ARI is infection of any part of the respiratory tract lasting < 30 days. Upper ARI (URTI) involves nose, sinuses, pharynx, larynx — common cold, sinusitis, pharyngitis, tonsillitis, laryngitis, otitis media. Lower ARI (LARI) involves trachea, bronchi, bronchioles, alveoli — acute bronchitis, pneumonia, bronchiolitis, lung abscess.

Causes: Mostly viral (rhinovirus, RSV, parainfluenza, influenza, adenovirus, SARS-CoV-2) — 80-90% of URTI. Bacterial causes: Streptococcus pyogenes (pharyngitis), Streptococcus pneumoniae, Haemophilus influenzae (sinusitis, pneumonia), Bordetella pertussis, Mycoplasma pneumoniae.

Risk factors: smoking, indoor/outdoor air pollution, malnutrition, immunosuppression, asthma/COPD, overcrowding, daycare attendance. ARI kills approximately 4 lakh Indians annually — mostly children under 5 and elderly with comorbidities.

Upper ARI

Common cold (viral rhinitis): Rhinovirus most common. Nasal congestion, rhinorrhoea, sneezing, mild sore throat, low-grade fever, lasts 5-7 days. Symptomatic treatment — paracetamol, saline nasal drops, hydration. No antibiotics. Beware of secondary bacterial sinusitis (persistent symptoms > 10 days, facial pain, purulent nasal discharge).
Acute pharyngitis: Viral (80%) — rhinovirus, adenovirus, EBV (infectious mononucleosis). Bacterial (20%) — Group A Streptococcus (Centor criteria: fever, tonsillar exudate, tender anterior cervical lymphadenopathy, absence of cough). Treatment: Penicillin V 500 mg BD x 10 days OR single dose Benzathine Penicillin 12 lakh units IM. Amoxicillin alternative. Avoid azithromycin for strep pharyngitis — high resistance.
Acute sinusitis: Viral (90%) — same as common cold. Bacterial (10%) — persistent > 10 days, double worsening, facial pain, purulent nasal discharge. Antibiotic: Amoxicillin-clavulanate 625 mg TID x 7-10 days.
Acute otitis media: Common in children. S. pneumoniae, H. influenzae, M. catarrhalis. Ear pain, fever, bulging red tympanic membrane. Treatment: Amoxicillin 80-90 mg/kg/day x 5-10 days (children). Watchful waiting acceptable in mild cases > 2 years.
Acute laryngitis / croup: Viral (parainfluenza). Hoarseness, barking cough, stridor. Mild — humidified air, oral dexamethasone. Severe stridor — nebulised adrenaline, dexamethasone IV.

Lower ARI

Acute bronchitis: Inflammation of bronchi, usually viral (90%). Cough > 5 days, may produce sputum. Self-limiting — 2-3 weeks. No antibiotics. Symptomatic — bronchodilator if wheeze, paracetamol, hydration.
Pneumonia: Bacterial (S. pneumoniae, H. influenzae) or viral (influenza, RSV, SARS-CoV-2). See childhood pneumonia page for WHO IMCI classification and adult pneumonia on Medicine page.
Bronchiolitis: RSV most common. Children < 2 years. Wheeze, crackles, hyperinflation on CXR. Supportive — oxygen, hydration, suction. Bronchodilator trial if uncertain (asthma vs bronchiolitis). Ribavirin for severe immunocompromised.
Influenza: Sudden high fever, myalgia, sore throat, headache. Oseltamivir 75 mg BD x 5 days within 48 hours of symptom onset — high-risk patients (pregnancy, elderly, comorbidities, healthcare workers).
COVID-19: SARS-CoV-2. Spectrum from asymptomatic to severe pneumonia/ARDS. Treatment per current MoHFW guidelines — symptomatic, antivirals (Molnupiravir, Favipiravir in early disease), steroids for hypoxia, anticoagulation for severe disease.
Lung abscess: Localised collection of pus in lung. Aspiration risk (alcohol, seizure, stroke). Treatment: IV Clindamycin or Ampicillin-sulbactam x 4-6 weeks. Drainage if large (> 6 cm) or not responding.

Antibiotic Stewardship

Most ARIs are viral and do NOT need antibiotics. Antibiotic misuse drives antimicrobial resistance — a critical public health threat in India. Antibiotics indicated only for:

Group A strep pharyngitis (Centor score ≥ 3)
Bacterial sinusitis (persistent > 10 days, double worsening, purulent discharge + facial pain)
Acute otitis media in children < 2 years or with severe symptoms
Pneumonia (clinical diagnosis + chest X-ray confirmation)
Pertussis (within 3 weeks of cough onset)
Severe acute exacerbation of COPD (Anthonisen criteria: increased sputum purulence + volume + dyspnoea)

Common pitfalls: antibiotics for viral upper respiratory infection, antibiotics for acute bronchitis in otherwise healthy adults, broad-spectrum antibiotics for uncomplicated pneumonia. Each inappropriate antibiotic prescription contributes to resistance that kills 5 lakh Indians annually.

Frequently Asked Questions

When do you need antibiotics for sore throat?

Only for Group A Streptococcal pharyngitis, which causes 20% of adult pharyngitis. Use Centor criteria: fever, tonsillar exudate, tender anterior cervical lymphadenopathy, absence of cough — score 3-4 suggests strep, treat with Penicillin V 500 mg BD x 10 days OR single dose Benzathine Penicillin 12 lakh units IM. Avoid azithromycin — high resistance. Viral pharyngitis (80%) — symptomatic treatment only.

What is the difference between acute bronchitis and pneumonia?

Acute bronchitis is inflammation of bronchi, usually viral, presents with cough > 5 days ± sputum, normal chest X-ray. Self-limiting, no antibiotics. Pneumonia is infection of lung parenchyma (alveoli), presents with fever, cough, dyspnoea, chest pain, focal crackles on auscultation, infiltrate on chest X-ray. Requires antibiotics — outpatient (oral Amoxicillin or Doxycycline) or inpatient (IV Ceftriaxone ± Azithromycin) based on severity.

When is Oseltamivir indicated for influenza?

Within 48 hours of symptom onset for: confirmed or suspected influenza in high-risk patients (pregnancy, age > 65, age < 2, comorbidities like asthma, COPD, heart disease, diabetes, immunosuppression, neurological disorders), severe progressive disease, hospitalised patients with influenza regardless of duration. Dose: 75 mg BD x 5 days (adult). Treatment beyond 48 hours still helps severe cases.

What is the Centor criteria for strep throat?

4 criteria — Fever, Exudate on tonsils, tender anterior cervical Lymphadenopathy, absence of Cough. Score 0-1: no testing, no antibiotics. Score 2: rapid strep test or throat culture. Score 3-4: empiric antibiotics (Penicillin V or Amoxicillin). Avoid macrolides (azithromycin) for strep throat due to high resistance rates in India.

How do you prevent acute respiratory infections?

Hand hygiene (soap and water or alcohol-based), avoid close contact with sick people, wear mask in crowded settings during flu season, annual influenza vaccine for high-risk groups (elderly, healthcare workers, pregnant women, chronic disease), pneumococcal vaccine (PCV13 + PPSV23) for elderly and immunocompromised, COVID-19 vaccination, smoking cessation, reduce indoor air pollution (LPG, ventilation).

Conclusion

ARI is the bread-and-butter of clinical practice — and the battleground for antibiotic stewardship. For UPSC CMS aspirants, distinguishing viral from bacterial ARI, Centor criteria, and oseltamivir indications are highly testable topics.

🎓 Explore More on CMS Prep

CMS Prep covers UPSC CMS previous year questions, NEET PG, INICET, FMGE, AFMS, and complete careers-after-MBBS guidance — all free, no login.

Practice UPSC CMS PYQs →Careers After MBBS Quick Links