Clinical Pearl Series from Yale-G First Aid: Crush USMLE Step 2CK & Step 3 by Yale Gong, MD, Sr. Medical Advisor at www.medicine.net (Copyrighted)

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Upper respiratory tract infections (URIs) are the most common diseases we encounter in our daily lives, including pharyngitis, laryngitis, the common cold, influenza, and COVID, etc., mostly caused by viruses, which include rhinoviruses, adenovirus, coronaviruses, coxsackievirus, influenza virus, and parainfluenza virus. Lower respiratory tract infections (LRIs) mainly refer to bronchitis (mostly by viruses) and pneumonia (mostly by bacteria). Viruses that cause LRIs include influenza A, B, adenovirus, H1N1, respiratory syncytial virus, parainfluenza virus, and coronaviruses.

1. What Is Pharyngitis and Its Diagnostic and Therapeutic Features?

Pharyngitis is inflammation of the pharynx, also known as “sore throat” and mostly caused by viruses (adenovirus, parainfluenza, rhinovirus, and E-B virus). However, Group-A Strep (S. pyogenes) infections (accounting for up to 15%) are more concerned because of the risk of developing rheumatic fever or glomerulonephritis.

Essentials of diagnosis

(1)Viral pharyngitis mostly shows fever, cough, and rhinorrhea instead of exudates, except E-B virus.

(2)Sore red throat, tonsillar exudates, tender anterior cervical adenopathy, fever and absence of cough are highly suggestive of Strep pyogenes. Mild infections may not show exudates.

(3)Rapid antigen detection test (RADT) is the best initial testing with high sensitivity and specificity for bacterial pharyngitis. Positive Strep test result means the same as positive throat culture result, whereas a negative Strep test may require a confirmative throat culture if suspicion remains high. A throat culture is the gold-standard (most accurate) test but it takes 24-48 hours to yield results.

Treatment

(1)Most cases are viral and treated for symptomatic relief instead of antibiotics. Local therapies such as throat sprays and lozenges (with local anesthetics), a nonsteroidal anti-inflammatory drug (NSAID) and a short term of glucocorticoids (if severe) may be helpful.

(2)If it’s confirmed Strep pharyngitis, oral penicillin V for 10 days is the best treatment. Macrolides and 2nd-generation cephalosporins are alternatives for patients with penicillin allergy. For the rare case of an erythromycin-resistant strain when patient is unable to tolerate beta-lactam agents, clindamycin is an appropriate choice.

(3)If it’s mononucleosis, have rest and a NSAID (e.g., ibuprofen).

2. What Is Laryngitis and Its Clinical Features?

It is inflammation of the larynx usually caused by viruses, but maybe also by Moraxella catarrhalis and H. influenza. Patient commonly presents with hoarseness, cough, and other URI symptoms. Laryngitis is mostly self-limited and patient only needs symptomatic treatment (similar to that for viral pharyngitis) and voice rest.

Note: Shortness of breath, stridor, persistent cough, hemoptysis, throat pain, difficulty swallowing, unilateral otalgia, and weight loss in a patient with voice symptoms raise concern for cancer.

3. What Is The Common Cold and Its Diagnostic, Therapeutic and Preventive Features?

The “common cold” is the most common upper respiratory tract infection (URI). Susceptibility depends on pre-existing antibody level. Most organisms are viral. Rhinovirus accounts for > 50% of cases and have > 100 antigenic serotypes. Thus reinfection with another serotype are very common and can cause similar symptoms, since there is no cross-immunity among the serotypes.

Clinical features, diagnosis, and treatment

(1)Rhinorrhea, sore throat, nasal congestion, non-productive cough, and malaise. Fever may or may not be present.

(2)Most cases resolve in 5-7 days regardless of treatment. Symptomatic and supportive treatment and NSAIDs are adequate therapies in most cases if needed. Avoid abuse of antibiotics.

(3)Transmission is mostly by respiratory and hand-to-hand contact. Prolonged infection can lead to secondary bacterial infections such as sinusitis and pneumonia (in immunosuppressed patient). Best prevention is by regular exercise to increase immunity.

4. What Is Influenza (“Flu”) and Its Diagnostic, Therapeutic and Preventive Features?

“Flu” is a common systemic viral infection caused by influenza A, B, or C (belonging to the orthomyxovirus family) mainly through respiratory droplet nuclei. Only type A and B cause a human disease of any concern. It’s characterized by strong infectability, rapid transmission, and an epidemic pattern. Influenza can cause damage to the respiratory tract epithelium, leading to complications such as sinusitis, otitis media, bronchitis, and pneumonia. Annual epidemics are due to minor genetic changes in the viral (protein) structure and usually are not life-threatening except in immunocompromised and very young or old patients. Rare large regional or global pandemic outbreaks are due to major genetic reassortment and are often fatal.

Essentials of diagnosis

(1)Common presentations: Systemic symptoms of fever, chills, myalgias, headache, and fatigue; upper respiratory symptoms of coryza, dry cough, sore throat, and conjunctival injection.

(2)Rapid antigen detection of swabs or washings is the best initial test for diagnosis. Viral culture is the most accurate test but it takes a few days to show results.

Treatment

(1)Effective specific antiviral drugs for both influenza A and B are oseltamivir and zanamivir, and are recommended for all individuals with confirmed or suspected influenza who are severely ill (with dyspnea, tachypnea) or showing signs of rapid deterioration. Baloxavir marboxil is a new medicine for acute uncomplicated influenza in patients older than 12. These antiviral drugs help inhibit the viral replication and spread, and limit the symptomatic duration if used within 48 hours after onset. If it’s > 48 hours, give symptomatic treatment only (acetaminophen, antitussives, etc.). Amantadine and rimantadine are no longer recommended due to the high rates of influenza resistance.

(2)All pregnant women with suspected or confirmed influenza should use oseltamivir or zanamivir, even those who present >48 hours after onset provided that they are not yet improving.

Prevention

(1)Annual influenza vaccination (IIV, inactivated influenza): Since 2010, it has been recommended to everyone from 6 months of age on. There is also cross-protection against some different strains of virus (including novel viruses). It’s contraindicated in patients with severe allergic reaction (e.g., anaphylaxis) after previous dose or ingestion of egg protein. Benefits: Influenza vaccine has been demonstrated to significantly reduce the disease, hospitalization, and death in numerous studies. It’s especially beneficial to those with high risk.

(2)Postexposure prophylaxis: WHO recommends that household contacts of patients with H₅N₁ avian influenza should receive postexposure prophylaxis with 75 mg of oseltamivir once daily for 7-10 days.

5. What Are Coronaviruses and Its Diagnostic, Therapeutic and Preventive Features?

Coronaviruses are important human and animal pathogens, accounting for 5-10% community-acquired URIs in adults and probably also playing a role in severe LRIs, particularly in immunocompromised patients and primarily in the winter. 

Virology: Medium-sized enveloped positive-stranded RNA viruses as a family within the Nidovirales order. Severe types included severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and novel coronavirus (2019-nCoV, which causes COVID-19).

Routes of transmission: Similar to that of rhinoviruses, via direct contact with infected secretions or large aerosol droplets. Immunity develops soon after infection but wanes gradually over time. Reinfection is common.

Clinical manifestations and diagnosis

(1)Coronaviruses mostly cause respiratory symptoms (nasal congestion, rhinorrhea, cough) and influenza-like symptoms (fever, headache).

(2)Severe types (2019-nCoV, MERS-CoV, and SARS-CoV): Typically with pneumonia--fever, cough, dyspnea, and bilateral infiltrates on chest imaging, +/- enterocolitis (diarrhea), particularly in immunocompromised hosts (HIV+, elders, children).

(3)Most community-acquired coronavirus infections are diagnosed clinically and with an immunologic testing kit. RT-PCR can be confirmative if necessary.

Treatment

(1)It mainly consists of ensuring appropriate control of infection and symptoms and supportive care for sepsis and acute respiratory distress syndrome (oxygen, IMV, etc.).

(2)Clinical trials: Chloroquine showed activity against the SARS-CoV, HCoV-229E, and HCoV-OC43, and remdesivir, etc against 2019-nCoV. Dexamethasone may have clinical benefit in severe cases.

Prevention:

(1)Diligent hand washing, respiratory hygiene, and avoiding close contact with live or dead animals and ill individuals.

(2)Wear a medical mask to contain their respiratory secretions and seek medical attention; standard contact and airborne precautions, with eye protection.

(3)New promising vaccines for COVID-19, including mRNA based and viral vector vaccines, are recommended for most adults without special conditions. Be alert for some rare complications such as vaccine-induced immune thrombotic thrombocytopenia and myocarditis, and increased resistance to the Delta Omicron variant, etc.