Similarities and differences between Coronavirus (COVID-19), Influenza and Common Cold

Seasonal flu (Influenza) and colds (RSV) are respiratory infections with a main period of occurrence in the winter months. This list of viruses now gets updated with coronavirus SaRs-CoV-2 which causes the disease known as COVID-19. Separating these viral infections is difficult even for the most expert clinicians if there is no laboratory diagnosis. The above viruses cause respiratory disease, however they have important differences between them.

Similarities between COVID-19 and Flu

The COVID-19 and influenza viruses have a similar disease presentation. Both viruses attack the respiratory system and show a wide range of symptoms, from asymptomatic or mild to severe illness and death.

Both viruses get transmitted through contact and droplets. As a result, the same public health measures, such as hand hygiene and coughing/sneezing into your elbow or a tissue and disposing of it immediately, are important actions that everyone can take to prevent infection.
There is an incubation period of the disease for both viruses before the first symptoms appear, and the infected person can transmit the virus while being asymptomatic.

Differences between COVID-19 and Flu

Transmission speed is a major point of difference between the two viruses. Influenza has a shorter median incubation period (the time from infection to the onset of symptoms) and a shorter serial interval (the time between consecutive cases) than the COVID-19 virus.

The flu can spread faster than COVID-19. The serial interval for the COVID-19 virus is estimated to be 5-6 days, while for the influenza virus, the serial interval is 3 days.

In addition, transmission during the first 3-5 days of illness or possibly pre-symptomatic transmission – transmission of the virus before symptoms appear – is an important factor in flu transmission. Instead, we are learning that there are people who can transmit the COVID-19 virus 24-48 hours before the onset of symptoms, for now, this does not appear to be a significant factor in transmission.

The basic reproduction number – the number of secondary infections generated by an infected person – is thought to be between 2 and 2.5 for the COVID-19 virus, higher than that of the flu. However, estimates for both COVID-19 and influenza viruses are highly environment- and time-specific, making direct comparisons more difficult.

Children are important agents of influenza virus transmission in the community. For the COVID-19 virus, initial data show that children are less affected than adults and that clinical attack rates in the 0-19 age group are low.

While the range of symptoms for the two viruses is similar, the proportion of people with severe disease appears to be different. For COVID-19, data to date suggest that 80% of infections are mild or asymptomatic, 15% are severe infections, requiring oxygen, and 5% are critical infections, requiring ventilation. These rates of severe and critical infection for COVID-19 are higher than those seen for influenza infection.

Those most at risk of severe flu infection are children, pregnant women, the elderly, people with underlying chronic medical conditions, and those who are immunocompromised. For COVID-19, our current understanding is that older age and underlying conditions increase the risk of severe infection.

Mortality for COVID-19 appears higher than for influenza, especially seasonal influenza. While the true mortality of COVID-19 will take some time to fully understand, data we have so far shows that the gross mortality rate (the number of reported deaths divided by the reported cases) is between 3-4%, the infection mortality (the number of reported deaths by the number of infections) will be lower. For seasonal flu, mortality is usually well below 0.1%. However, mortality is largely determined by access to and the quality of health care.

Treatments against COVID-19 and influenza

Although there are several therapeutic substances in clinical trials in China and more than 20 vaccines in development for COVID-19, there are currently no approved vaccines or therapeutics for COVID-19. In contrast, antivirals and vaccines are available for the flu. In patients one year of age and older with typical flu symptoms, the drug oseltamivir phosphate (Tamiflu) has been shown to be effective when treatment starts within two days of the first onset of symptoms. This indication is based on clinical studies of naturally occurring influenza, in which the predominant infection was influenza A.

While the flu vaccine is not effective against the COVID-19 virus, it is highly recommended that you get vaccinated each year to prevent influenza infection.

Table of differences between respiratory viruses: Flu, Cold (RSV) and Coronavirus

Common Cold – Respiratory Virus ( RSV )

The common cold is caused by a variety of viruses, with the main representatives being rhinoviruses (RV) and respiratory syncytial virus (RSV). RV appears to be responsible for 20-40% of cases of the common cold, while RSV accounts for 20%. They are transmitted in a similar way to the flu. The RSV virus is particularly important for children, according to the CDC approximately 57,000 children under the age of five are hospitalized each year worldwide from RSV infection. The most characteristic symptom of RSV in children is wheezing when breathing.

Conclusions

As COVID-19 and influenza are different viruses, they can cause similar symptoms. By all accounts, the symptoms of COVID-19 are more similar to those of the flu than the common cold. Due to the similarities of the symptoms, the diagnosis of the disease can only be made through laboratory tests.

Available Tests for diagnosis from Startbio (Molecular Diagnosis)

Specialized tests (molecular detection by RT-QPCR) for respiratory viruses are available in various combinations. You can choose the right test for you from the options below:

Stella Taka

Η Δρ. Στέλλα Τάκα (Styliani Taka) είναι μοριακός βιολόγος με πολυετή ερευνητική δραστηριότητα ως μεταδιδακτορική ερευνήτρια στο εργαστήριο Αλλεργιολογίας και Κλινικής ανοσολογίας, της Β΄ Παιδιατρικής Κλινικής, του Εθνικού και Καποδιστριακού Πανεπιστημίου Αθηνών (ΕΚΠΑ). Τα τελευταία χρόνια οι κύριες ερευνητικές της δραστηριότητες επικεντρώθηκαν στην αλληλεπίδραση μεταξύ των ανθρώπινων αναπνευστικών παθογόνων (ιών και βακτηρίων), και της φυσικής ανοσίας τόσο σε υγιείς όσο και σε αλλεργικούς ασθενείς. Έχει συμμετάσχει ως κύρια ερευνήτρια σε ευρωπαϊκά προγράμματα: NANOMYC, MIDAS, PREDICTA, iFaam, CURE. Έχει περισσότερα από 25 επιστημονικά άρθρα (h-index 8) και πάνω από 200 αναφορές , και είναι μία από τους εφευρέτες (Inventors) της πατέντας (Application number: 12001210.9) «Detection of leishmania».  Είναι  ενεργό μέλος της Ευρωπαϊκής Ακαδημίας Αλλεργιολογίας και Κλινικής Ανοσολογίας – EAACI. Με τον τομέα της διάγνωσης, ασχολείται από το 2009, ως υπεύθυνη του μοριακού ελέγχου, κυρίως μέσω των γενετικών και μοριακών αναλύσεων διάφορων ασθενειών όπως η κυστική ίνωση, η θρομβοφιλία, τα σεξουαλικώς μεταδιδόμενα νοσήματα και τα τελευταία χρόνια από το 2012 και μετά κυρίως με τις αλλεργίες και τα παθογόνα του αναπνευστικού. Περισσότερα για το ερευνητικό έργο της Στέλλα Τάκα στα Google Scholar και ResearchGate.