Flu and COVID-19: How Do the Illnesses Compare?

The two share a lot of similarities, but there are key differences between them.

It’s a common occurrence for a set of symptoms to potentially indicate a variety of distinct conditions or ailments. This can often lead to challenges in accurately identifying the specific illness, disorder, syndrome, or infection afflicting an individual.

In March 2020, the declaration of COVID-19 as a global pandemic brought about the necessity to differentiate between influenza and COVID-19 infections. The concerted endeavors to mitigate the transmission of COVID-19 had an unintended positive effect of reducing the prevalence of certain viral respiratory pathogens, including those responsible for causing influenza.

In this context, expert opinions from infectious disease specialists are shared to facilitate a comparative analysis of influenza and COVID-19. This guidance aims to empower individuals to proactively manage their well-being and contribute to the safeguarding of their local communities.

What Are the Similarities Between COVID-19 and the Flu?

COVID-19 and influenza exhibit a multitude of shared characteristics. Predominantly, they both manifest as respiratory ailments, targeting the respiratory tract as their primary point of infection, as outlined by Nicolas Barros Baertl, MD, an infectious disease expert associated with Indiana University Health.

Beyond this fundamental aspect, these two viruses also present comparable sets of symptoms, transmission mechanisms, and preventive measures.

Symptoms

As both influenza and SARS-CoV-2 (the causative agent of COVID-19) predominantly affect the respiratory system, they often lead to the emergence of comparable symptoms. A comprehensive assessment has highlighted that the most frequently observed symptoms in both conditions include fever and cough.

Nevertheless, the following symptoms might manifest in cases of either influenza or COVID-19:

• Fever and chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Sore throat
• Runny or congested nose
• Muscle pain or bodily discomfort
• Headache
• Vomiting and diarrhea (more commonly found in children affected by either influenza or COVID-19)
• Alteration in, or loss of, taste and smell (more prevalent in instances of COVID-19)

It’s noteworthy that an individual could be afflicted with either ailment and experience a range of symptoms, varying from an absence of symptoms to the presence of several severe manifestations.

How the Viruses Spread

In the realm of respiratory infections, the modes of transmission for both COVID-19 and influenza primarily involve the transmission of infected respiratory particles from one individual to another. Richard Zimmerman, MD, a distinguished figure in medicine and public health at the University of Pittsburgh and a practitioner of family medicine, affirms this point.

Transmission occurs predominantly through close interactions with infected individuals, particularly when an afflicted person expels infected droplets via coughing or sneezing, which can subsequently be inhaled by nearby healthy individuals. While the primary mode of transmission is direct contact with individuals, it’s important to note that both viruses also have the potential to spread through contact with contaminated surfaces or objects.3

It’s worth noting that while the likelihood of transmission is heightened when an individual is already symptomatic, Dr. Zimmerman indicates that both viruses are also capable of:

1. Asymptomatic transmission, where an individual is infected but displays no symptoms.

2. Pre-symptomatic transmission, occurs before a symptomatic individual starts showing signs of illness.

3. Transmission from individuals with mild symptoms that may be hardly noticeable.

Prevention

Both COVID-19 and influenza possess vaccines designed to mitigate the severity of the illnesses. While no vaccine provides absolute immunity, those sanctioned for usage, as well as those granted emergency authorization, exhibit a substantial capability to significantly diminish hospitalization rates and fatalities. Moreover, individuals aged six months and beyond are eligible candidates for vaccination against both the flu and COVID-19.

In the context of influenza, the US Food and Drug Administration (FDA) endorses multiple licensed vaccines produced annually, tailored to combat the anticipated circulation of four specific flu viruses. This characteristic leads to the nomenclature of these vaccines as quadrivalent influenza vaccines.

As of November 2022, the FDA has granted approval or emergency use authorization to four COVID-19 vaccines:

• Pfizer-BioNTech
• Moderna
• Johnson & Johnson
• Novavax

Beyond vaccinations, effective preventive measures encompass practices such as wearing masks, practicing frequent hand hygiene, and maintaining physical distance from large gatherings. Dr. Zimmerman underscores the efficacy of masking, emphasizing its impact on both COVID-19 and influenza. He cites this as a contributing factor to the marked decline in influenza cases during 2020.

What Are the Differences Between COVID-19 and the Flu?

While both viruses predominantly induce respiratory ailments, they are inherently distinct entities.

Influenza, commonly known as the flu, stems from influenza viruses, comprising two primary human-impacting types: influenza A and influenza B viruses.

Influenza A viruses are further classified into subtypes denoted by hemagglutinin (H) and neuraminidase (N), each with a multitude of potential combinations. Meanwhile, influenza B viruses are categorized into lineages: B/Yamagata and B/Victoria.6

Conversely, COVID-19 is attributed to the SARS-CoV-2 virus, a member of the coronavirus family. Coronaviruses usually trigger mild to moderate respiratory tract illnesses, akin to the common cold. Nonetheless, COVID-19 stands alongside severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) as one of the three coronaviruses that have elicited significant global or widespread severe illnesses.

Moreover, flu symptoms typically manifest within one to four days post-exposure. In contrast, the incubation period for COVID-19 can extend up to 14 days before symptoms materialize. However, the contrasts between these two illnesses extend beyond these points.

Complications

COVID-19 and influenza often manifest with a shared array of symptoms. Moreover, both can give rise to instances involving:

• Pneumonia
• Respiratory failure
• Acute respiratory distress syndrome (ARDS)

However, COVID-19 has the capacity to impact various other organ systems within the body to a greater extent than the flu, as highlighted by James H. Conway, MD, a distinguished pediatric infectious disease specialist and associate director for health sciences at the Global Health Institute of the University of Wisconsin-Madison.

While secondary bacterial infections, such as sinus and ear infections, can emerge in individuals with COVID-19 and the flu, the likelihood of developing a bacterial infection is more pronounced in cases of influenza.

COVID-19 infections exhibit a higher prevalence of blood clot formation in veins and arteries across the lungs, heart, legs, and brain compared to flu cases. The illness can also lead to a condition known as multisystem inflammatory syndrome, characterized by inflammation affecting various body parts like the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs.

A distinctive complication unique to COVID-19, absent in flu cases, is the emergence of Long COVID. This syndrome encompasses an array of symptoms, including:

• Fatigue
• Cognitive impairment (often referred to as “brain fog”)
• Heart palpitations
• Headaches
• Muscle aches

These symptoms can persist for weeks or even months after the initial viral infection, even if the initial symptoms were mild. Overall, Dr. Conway emphasizes that COVID-19 demonstrates a broader impact on various bodily organs compared to influenza.

Infections and Deaths

The global impact of COVID-19, as reported by the World Health Organization’s (WHO) COVID-19 dashboard, reveals an unsettling reality: numerous confirmed cases, amounting to hundreds of millions, and a staggering number of fatalities.

Within the United States, the toll of COVID-19 is equally stark, with over 97 million confirmed cases and an unfortunate count of more than one million deaths. It’s important to acknowledge that these figures only encompass confirmed cases, potentially underestimating the true magnitude due to individuals who may have experienced symptoms but refrained from seeking medical attention.

Shifting our focus to influenza, the worldwide landscape witnesses an estimated annual occurrence of one billion cases, accompanied by a substantial toll of up to 650,000 deaths attributed to influenza-related complications.10 Specifically, within the United States, the Centers for Disease Control and Prevention (CDC) estimates the annual flu burden to range between nine million and 41 million illnesses, contributing to 12,000–52,000 deaths each year.

In the grander scheme, COVID-19 distinctly exhibits a higher fatality rate than the flu, with a greater propensity to induce severe illness and necessitate hospitalization. Elaborating on this, Dr. Barros elucidates that the case fatality rate for COVID-19 stands at 0.2%, in stark contrast to influenza’s 0.01% case fatality rate.

Treatments

Antiviral drugs serve as a viable treatment avenue for influenza, and the FDA has granted approval to four of these medications:

1. Tamiflu (oseltamivir phosphate)

2. Relenza (zanamivir)

3. Rapivab (peramivir)

4. Xofluza (baloxavir marboxil)

These antivirals are most effective when administered promptly, ideally within approximately two days of the onset of flu symptoms.3

Notably, not everyone necessitates antiviral treatment for the flu. Generally, individuals who are healthy and devoid of risk factors for complications can effectively manage flu symptoms through conventional home remedies, such as rest, hydration, and fever-reducing measures. Nevertheless, individuals with severe illness that doesn’t warrant hospitalization or those with mild symptoms but at an elevated risk of complications might benefit from antiviral intervention.

Conversely, as of November 2022, two FDA-approved drugs stand available for treating COVID-19: remdesivir (sold as Veklury) and baricitinib (branded as Olumiant).

The FDA guidelines recommend remdesivir for pediatric and adult patients who have tested positive for COVID-19. This includes individuals who are either hospitalized or not hospitalized but manifest mild-to-moderate COVID-19 with a substantial risk of progression towards severe forms of the illness.12

It’s important to note that for pediatric patients to be eligible for remdesivir treatment, they must be at least 28 days old and weigh at least 3 kilograms (approximately 6.5 pounds). Baricitinib, on the other hand, is recommended for administration to hospitalized patients who require supplementary oxygen.

Furthermore, the FDA has issued Emergency Use Authorizations (EUAs) for diverse categories of treatments for COVID-19. These encompass monoclonal antibody (mAB) products, antiviral drugs (like Paxlovid), immune modulators, sedatives, and renal replacement therapies for specific populations.

While acquiring antiviral medications for the flu is relatively straightforward, the landscape of treatment options for COVID-19 is notably more intricate. “It’s not quite the same as dropping by your doctor’s office to get a prescription,” Dr. Zimmerman remarked.

A Quick Review

In conclusion, a multitude of similarities and distinctions exist between COVID-19 and the seasonal flu. Should you harbor any inquiries or apprehensions about either of these illnesses, spanning facets like symptoms or treatment alternatives, seeking guidance from a healthcare professional is recommended for comprehensive and accurate information.