The “Wuhan flu” describes a global health crisis that emerged in late 2019. It rapidly evolved from a localized outbreak to a widespread phenomenon, impacting societies and economies.
Understanding the Disease
The illness known as the “Wuhan flu” is Coronavirus Disease 2019 (COVID-19). It is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), a virus in the coronavirus family.
Coronaviruses are diverse RNA viruses infecting animals and humans. Named for their crown-like surface spikes, some cause mild illnesses like the common cold. Others, like SARS-CoV-2, lead to severe respiratory conditions.
The Outbreak’s Genesis
The “Wuhan flu” emerged in Wuhan, China, in December 2019. Early investigations focused on the Huanan Seafood Wholesale Market, where many initial cases were linked to visitors.
Scientific consensus suggests a zoonotic origin: the virus likely jumped from animals to humans. SARS-CoV-2 is closely related to coronaviruses in bats and pangolins. Live mammals susceptible to coronaviruses were sold at the Huanan market before the pandemic. This environment could have facilitated transmission from an animal host to humans, potentially via an intermediate animal.
Modes of Transmission
SARS-CoV-2 primarily spreads person-to-person via respiratory droplets and aerosols. Infected individuals release tiny virus-containing particles into the air when coughing, sneezing, talking, singing, or breathing. These particles can be inhaled or contact mucous membranes in the eyes, nose, or mouth.
Infection risk increases with closer contact and longer exposure, especially in poorly ventilated or crowded indoor settings. Less commonly, transmission occurs if a person touches contaminated surfaces and then their face without washing hands. Infected individuals can spread the virus before symptoms appear (asymptomatic transmission). The incubation period, from exposure to symptom onset, ranges from 2 to 14 days, averaging about 5 days.
Clinical Manifestations
Individuals infected with SARS-CoV-2 experience a broad spectrum of symptoms, from very mild to severe. Common symptoms include fever, chills, cough, fatigue, headache, muscle aches, sore throat, congestion, runny nose, nausea, vomiting, and diarrhea. A notable symptom was new loss of taste or smell.
Most people develop mild to moderate symptoms, while others experience severe symptoms like difficulty breathing, shortness of breath, or pneumonia. Complications include acute respiratory distress syndrome (ARDS), blood clots, heart inflammation, kidney injury, and multisystem inflammatory syndrome in children (MIS-C). Some also develop “long COVID,” with symptoms persisting for weeks, months, or years after initial infection.
Global Progression
The “Wuhan flu” transitioned to a global pandemic. After appearing in Wuhan in December 2019, the virus spread within China. By January 2020, confirmed cases were reported in other countries, including Thailand, Japan, and South Korea.
The World Health Organization (WHO) declared the outbreak a Public Health Emergency of International Concern (PHEIC) on January 30, 2020, recognizing its potential for international spread and need for a coordinated global response. The WHO assessed the outbreak as a pandemic on March 11, 2020, as the virus continued global expansion.