Severe Acute Respiratory Syndrome: Symptoms, Types, Causes and Treatment

Severe Acute Respiratory Syndrome (SARS) has reshaped how the world views respiratory viral outbreaks. Since its dramatic emergence in the early 2000s, SARS and its related viruses have sparked global concern, rapid scientific collaboration, and a race to understand its symptoms, types, causes, and optimal treatments. This article provides a comprehensive, evidence-based overview drawn from major outbreak studies, clinical observations, and the latest research on SARS and its relatives.

Symptoms of Severe Acute Respiratory Syndrome

Severe Acute Respiratory Syndrome (SARS) is notorious for its abrupt onset and rapid progression. Recognizing its symptoms early is crucial for patient care and limiting outbreaks. SARS typically starts with nonspecific flu-like symptoms, but it can quickly advance to severe respiratory compromise. Below, we summarize the most frequently reported symptoms and clinical features.

Symptom	Prevalence	Clinical Significance	Source
Fever	Nearly all patients	Early indicator, universal	1 2 3 4 6
Cough	>50% (dry, nonproductive)	Key respiratory symptom	1 2 4 5 6
Myalgia	~60%	Early systemic sign	1 3 6
Dyspnea	50–80%	Signals respiratory progression	2 3 4
Headache	>50%	Common, but nonspecific	1 2
Diarrhea	Up to 24%	Gastrointestinal involvement	3 5
Malaise	~70%	General feeling of unwellness	2 4
Lymphopenia	>70% (lab finding)	Marker of severity	1 2 4 5 6

Table 1: Key Symptoms of SARS and Related Illnesses

Early and Common Symptoms

The earliest and most consistent symptom of SARS is a high fever, often above 38°C, which may be accompanied by chills and rigors. Many patients also report significant muscle pain (myalgia), malaise, and headache—signs that are common to many viral illnesses but particularly prominent in SARS outbreaks 1 2 3 4.

Respiratory Manifestations

SARS is, at its core, a respiratory illness. A dry, nonproductive cough typically develops within a few days of fever onset. This may progress to shortness of breath (dyspnea), and in severe cases, patients exhibit hypoxemia and require supplemental oxygen 2 3 4 5. Notably, in some cohorts, crackles and percussion dullness were detected on chest examination—a sign of underlying lung involvement 2.

Gastrointestinal and Systemic Features

While less frequent, gastrointestinal symptoms, including diarrhea, have been reported in up to a quarter of patients 3 5. Malaise—an overwhelming sense of fatigue and weakness—is also common, reflecting the systemic nature of the infection 2 4.

Laboratory and Radiographic Findings

Laboratory testing often reveals lymphopenia (a reduced lymphocyte count), thrombocytopenia, and elevated liver enzymes—markers that help gauge severity 1 2 4 5 6. Imaging studies frequently show patchy or bilateral air-space consolidation, even when respiratory symptoms are mild 1 3 5 6.

Types of Severe Acute Respiratory Syndrome

Over the past two decades, the term "Severe Acute Respiratory Syndrome" has evolved to encompass diseases caused by different coronaviruses. These types differ in their epidemiology, clinical course, and outcomes. Understanding these distinctions is essential for both clinicians and the public.

Type	Causative Virus	Outbreak Period	Key Features	Source
Classic SARS	SARS-CoV	2002–2003	High mortality, nosocomial spread	3 7 9
COVID-19	SARS-CoV-2	2019–present	Milder in most, rapid spread	5 8 12
Related Syndromes	MERS-CoV, others	2012–present (MERS)	Severe, less transmissible	8

Table 2: Types of Severe Acute Respiratory Syndrome

Classic SARS (SARS-CoV)

The original SARS outbreak, caused by the SARS coronavirus (SARS-CoV), emerged in southern China in 2002 and spread rapidly across continents 3 7. This form was characterized by high mortality (up to 10–15%), significant nosocomial (hospital-based) transmission, and a tendency to cause severe lower respiratory tract disease 1 3 7 9.

SARS-CoV-2 (COVID-19)

A new, genetically related coronavirus, SARS-CoV-2, was identified in late 2019 as the cause of the COVID-19 pandemic. While sharing similarities with classic SARS, COVID-19 often presents with milder symptoms in many cases but can cause severe pneumonia and acute respiratory distress syndrome (ARDS), particularly in high-risk groups 5 8 12. Its rapid, efficient human-to-human transmission distinguishes it from classic SARS 5 8.

Other Related Syndromes

Middle East Respiratory Syndrome (MERS), caused by MERS-CoV, shares features with both SARS-CoV and SARS-CoV-2 but is less transmissible and has a higher case fatality rate 8. The coronaviruses responsible for these syndromes are genetically related but differ in their patterns of transmission and severity.

Why the Distinction Matters

• Clinical management and public health strategies may vary depending on the causative virus.
• Understanding differences in transmission helps guide infection control measures.
• Vaccine and therapeutic development often target virus-specific features 8 10.

Causes of Severe Acute Respiratory Syndrome

SARS is fundamentally a viral illness, but understanding its exact causes, transmission pathways, and mechanisms of disease is critical for containment and treatment.

Cause	Description	Transmission Mode	Source
SARS-CoV	Coronavirus, novel to humans	Droplets, close contact	3 4 6 7 9
SARS-CoV-2	Novel coronavirus (COVID-19)	Airborne, droplets, fomite	5 8
Animal Reservoirs	Bats, civet cats (zoonotic origin)	Animal-to-human	3 8
Human-to-Human Spread	Nosocomial, community transmission	Aerosols, direct contact	1 3 4 5

Table 3: Causes and Transmission of SARS

The Viral Culprits: Coronaviruses

Both SARS and COVID-19 are caused by coronaviruses—a family of RNA viruses known for their crown-like appearance under the microscope. SARS-CoV was identified as the cause of the 2002–2003 SARS outbreak, while SARS-CoV-2 is responsible for COVID-19 3 4 6 7 8 9.

Zoonotic Origins

These viruses are believed to have originated in animals. SARS-CoV likely jumped from bats to civet cats and then to humans in live animal markets in southern China 3 8. Similarly, SARS-CoV-2 is suspected to have zoonotic origins, potentially from bats or intermediary animal hosts 8.

Modes of Transmission

• Human-to-Human: Transmission occurs mainly via respiratory droplets and close contact. Nosocomial (hospital-acquired) spread was a significant factor in SARS outbreaks, especially among health care workers 1 3 4 5.
• Airborne and Surface: For SARS-CoV-2, evidence suggests airborne spread and fomite transmission play a role, explaining its rapid global dissemination 5 8.
• Super-Spreader Events: Certain settings and procedures (e.g., aerosol-generating procedures) can amplify transmission, leading to clusters of cases 3 7.

Pathogenesis

Once inside the human body, these viruses target epithelial cells in the respiratory tract through the ACE2 receptor, leading to lung injury, dysregulated immune response (including cytokine storms), and potentially multi-organ involvement 8 9.

Why Understanding Causes Matters

• Guides infection control (e.g., isolation, quarantine)
• Informs vaccine and drug development
• Helps prevent future outbreaks by monitoring animal reservoirs 3 8

Treatment of Severe Acute Respiratory Syndrome

Managing SARS and related illnesses remains a significant challenge. Due to the lack of specific antiviral cures, treatment has focused on supportive care, experimental therapies, and rigorous infection control.

Treatment	Approach/Drug	Outcomes/Notes	Source
Supportive Care	Oxygen, fluids	Mainstay, critical cases	3 4 5
Corticosteroids	Methylprednisolone, others	Reduced mortality in severe cases	3 11 13
Antivirals	Ribavirin, oseltamivir	No proven benefit	2 4
Mechanical Ventilation	For ARDS/Resp. failure	Required in severe cases	3 4
Traditional Chinese Medicine (TCM)	Herbal therapies	Symptomatic relief, widely used in China	12

Table 4: Approaches to SARS Treatment

Supportive Care

The cornerstone of SARS treatment is supportive care, including oxygen supplementation, intravenous fluids, and monitoring for complications. In severe cases, patients may require intensive care management and mechanical ventilation 3 4 5.

Corticosteroids

Several studies have explored the use of corticosteroids (e.g., methylprednisolone) to dampen the hyperactive immune response seen in severe cases. Evidence suggests that early high-dose steroid regimens can reduce mortality and the need for invasive ventilation, particularly in critically ill patients 3 11 13. Pulse steroid therapy (high-dose for short duration) may offer better radiographic and clinical outcomes compared to lower-dose regimens 11 13.

• Caveats: Steroids should be used judiciously, as inappropriate use may lead to complications, including secondary infections 11 13.

Antiviral Agents

Empirical use of antivirals such as ribavirin and oseltamivir was common during the original SARS outbreak, but studies have not demonstrated convincing benefit 2 4. Research continues into targeted viral protease inhibitors, but no specific antiviral has yet proven highly effective against SARS-CoV or SARS-CoV-2 10.

Mechanical Ventilation and Advanced Support

Patients progressing to acute respiratory distress syndrome (ARDS) may require mechanical ventilation and intensive care management. Noninvasive ventilation (e.g., nasal CPAP) has been associated with improved outcomes when combined with early steroid therapy 3.

Traditional Chinese Medicine (TCM)

In China, TCM has been used extensively as an adjunct therapy for SARS-CoV and SARS-CoV-2 infections. While some studies and clinical experience suggest symptomatic benefits, robust evidence from large randomized trials is lacking 12.

Infection Control and Prevention

Strict infection control measures—rapid case identification, isolation, and personal protective equipment—are vital for stopping transmission, especially in healthcare settings. These strategies proved successful in containing SARS outbreaks 3 7.

Conclusion

Severe Acute Respiratory Syndrome represents a unique and ongoing challenge in infectious disease medicine. From its alarming symptoms to its diverse viral causes and evolving treatments, understanding SARS is crucial for clinicians, researchers, and the public alike.

Key Takeaways:

• Symptoms: Fever, cough, myalgia, and dyspnea are hallmark symptoms; laboratory findings like lymphopenia and abnormal chest imaging help confirm diagnosis 1 2 3 4 5 6.
• Types: Classic SARS-CoV (2002–2003), SARS-CoV-2 (COVID-19, 2019–present), and related syndromes differ in transmission and severity 3 5 7 8.
• Causes: Zoonotic coronaviruses are responsible, with human-to-human transmission primarily via droplets and close contact 3 4 5 6 7 8 9.
• Treatment: Supportive care is central; corticosteroids provide benefit in severe cases; infection control is vital; antivirals and TCM are under further study 3 4 5 10 11 12 13.

Understanding SARS not only helps us manage current outbreaks but also prepares us for future emerging respiratory viruses. Ongoing research and vigilant public health efforts are essential to minimize the impact of these formidable pathogens.