"I Thought It Was a Cold, but Is It the Flu?" How Can You Tell the Difference Between a Cold, the Flu, and COVID-19? [Health Talk]

[Financial News] As the number of influenza and COVID-19 patients rises sharply at the same time, failing to distinguish among a common cold, influenza, and COVID-19 based solely on early symptoms could mean missing the critical window for treatment.
According to the Korea Disease Control and Prevention Agency (KDCA), the influenza-like illness rate in the fourth week of August rose sharply to 13.3 cases per 1,000 outpatients, up from 9.2 the previous week and more than double the 6.4 recorded during the same period last year. The virus is spreading mainly among elementary school students aged 7 to 12 following the start of the school year, while the number of hospital-level inpatients with COVID-19 has also more than doubled in four weeks.
Influenza is an acute respiratory illness caused by influenza viruses. Infection can lead to a higher mortality rate among older adults, children, and people with underlying conditions, as well as complications such as pneumonia, making it important not to overlook the early symptoms.
Park Wan-beom, a professor of infectious diseases at Seoul National University Hospital, said, "Recently, there has been a noticeable increase in outpatients complaining of fever and cough." He emphasized, "To prevent influenza and respond quickly when symptoms are suspected, it is essential to accurately distinguish it from the common cold and COVID-19 and to undergo testing and vaccination in a timely manner."

Influenza differs from the common cold from the outset because it is caused by a different pathogen. While a cold usually begins gradually with a runny nose, sneezing, and a mild fever of 38°C or lower, influenza is characterized by the sudden onset of high fever, headache, chills, muscle aches, and general weakness. COVID-19 can resemble a cold, but changes in the sense of smell or taste may occur, and shortness of breath can develop as the illness progresses. These features can help distinguish among the three illnesses.
If a high fever lasts for three to four days or longer, does not come down even after taking fever-reducing medication, or is accompanied by severe respiratory symptoms such as shortness of breath, chest pain, or cyanosis in which the lips turn blue, patients should seek medical attention without delay.
In children, caregivers should closely watch for signs of dehydration, including lethargy or reduced responsiveness, refusal to drink fluids, and decreased urine output. If symptoms improve and then suddenly worsen again, a secondary infection such as bacterial pneumonia should be suspected. In addition, people at high risk of complications—including adults aged 65 or older, those with chronic illnesses, pregnant women, and infants under 2—should seek medical care early even if their symptoms are mild. Avoiding work or school and getting tested when fever or respiratory symptoms are present can also help reduce the spread of infection.

If left untreated, influenza can lead to serious complications. The most serious is pneumonia, which may be caused by the virus itself or develop through a secondary bacterial infection. Other possible complications include myositis, myocarditis, pericarditis, and neurological complications such as encephalitis.
In particular, children may develop Reye syndrome around the time their influenza symptoms begin to improve. They may suddenly experience vomiting, agitation, and severe neurological symptoms such as seizures. Because the condition is known to be associated with aspirin use, aspirin must never be given to children with fever or cold symptoms of unknown cause.

If influenza is suspected, a specimen should be collected at the time symptoms begin, or within four to five days at the latest for adults, to improve diagnostic accuracy. Rapid antigen tests can provide results in about 15 minutes, but their sensitivity may decline during periods of widespread transmission. If the result is negative despite clear symptoms, it is safer to confirm it with a molecular test, such as the more accurate real-time RT-PCR test, which takes six hours or more.
Antiviral drugs used for treatment, including Tamiflu, peramivir, and Baloxavir marboxil, are most effective when administered within 48 hours of symptom onset. However, people at high risk of complications should begin antiviral treatment even if more than 48 hours have passed.
This season's national influenza vaccination program will begin sequentially by age group and eligibility category on September 21, and eligibility has been expanded to include children up to 14 years old. Vaccinations for adults aged 65 and older will begin in mid-October, and COVID-19 vaccination can also be administered at the same time during this period.
Professor Park advised, "Because it is difficult to distinguish influenza, COVID-19, and the common cold perfectly based on symptoms alone, the most accurate approach is to get tested immediately if you suspect an infection." He added, "People in high-risk groups, such as older adults and those with underlying conditions, should not delay vaccination and should strictly follow basic infection-control measures, including wearing masks and practicing hand hygiene."
 
[email protected] Medical Specialist Jung Myung-jin Reporter