How you ever hear about the Spanish Flu also known as influenza virus?
Chances are most of you haven’t, The Spanish Flu started in 1918. It is known as the 1918 influenza pandemic and it was the most severe pandemic in recent history.
Due to the period it occurred, there is no universal consensus regarding where the virus originated, but fact-checkers agree it spread from 1918 to 1919.
In the United States, it was first identified in military personnel in spring 1918. It is estimated that about 500 million people or one-third of the world’s population became infected with this virus. The number of deaths was estimated to be at least 50 million worldwide with about 675,000 occurring in the United States.
Today 100 years later, it seems like History is repeating itself. The COVID-19 outbreak continues to spread it is easy to draw similarities especially the fact that they both cause respiratory disease. Represented with a wide range of illnesses from asymptomatic to severe symptoms and death.
Both Viruses are transmitted by contact, droplets and fomites. Sparking similar public respond to pay attention to hand hygiene (something we should always practice in the first place) but that’s a story for another day.
But the similarities end there.
The Transmission speed is the most important difference between both viruses. The Spanish flu has a much shorter incubation time before people start showing symptoms. The serial interval for COVID-19 virus is estimated to be 5-6 days, while for the influenza virus, the serial interval is 3 days. This means that influenza can spread faster than COVID19 (coronavirus).
Transmission in the first 3-5 days of illness, or potentially pre-symptomatic transmission –transmission of the virus before the appearance of symptoms – is a major driver of transmission for influenza. In contrast, while we are learning that there are people who can shed COVID-19 virus 24-48 hours before symptom onset, at present, this does not appear to be a major driver of transmission.
The reproductive number – the number of secondary infections generated from one infected individual – is understood to be between 2 and 2.5 for COVID-19 virus, higher than for influenza. However, estimates for both
COVID-19 (Coronavirus) and influenza viruses are very context and time-specific, making direct comparisons more difficult.
Children are important drivers of influenza virus transmission in the community. For COVID-19 virus, initial data indicate that children are less affected than adults and that clinical attack rates in the 0-19 age group are low.
Preliminary data from household transmission studies in China suggest that children are infected from adults, rather than vice versa.
While the range of symptoms for the two viruses is similar, the fraction 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 infection, requiring oxygen and 5% are critical infections, requiring ventilation. These fractions of severe and critical infection would be higher than what is observed for influenza infection.
Those most at risk for severe influenza infection are children, pregnant women, elderly, those with underlying chronic medical conditions and those who are immunosuppressed. For COVID-19 (Coronavirus), our current understanding is that older age and underlying conditions increase the risk for severe infection.
Mortality for COVID-19 (Coronavirus) appears higher than for influenza, especially seasonal influenza. While the true mortality of COVID-19 will take some time to fully understand, the data we have so far indicated that the crude mortality ratio (the number of reported deaths divided by the reported cases) is between 3-4%, the infection mortality rate (the number of reported deaths divided by the number of infections) will be lower. For seasonal influenza, mortality is usually well below 0.1%. However, mortality is to a large extent determined by access to and quality of health care.
Evaluating the Numbers
1918 flu pandemic
- R naught: about 1.8
- Mortality rate: 2.5%
- World population: 1.8 billion (est.)
- R naught: 2.0
- Mortality rate: 4.5% (this number is in flux)
- World population: 7.8 billion
The Mortality rate is not set in stone but as it stands it is already deadly than the Spanish flu and one of the deadliest pandemics in history. But with careful monitoring and regular updates, thanks to modern-day technology Humanity is more ready today than we were 100 years ago. But Note the most important update is Stay at Home and Stay Safe.
- CDC (cdc.gov)
- WHO (who.int)
Definition of Terms
1. The ‘R naught’: Scientists also assess the so-called R naught of the disease, a mathematical equation that shows how many people will get sick from each infected person.
2. The mortality rate: The mortality rate is an important metric for epidemiologists because it helps determine just how many people will likely die from a particular disease and its potential impact on health systems.
3. Suspect case: A patient with acute respiratory illness (fever and at least one sign/symptom of respiratory disease (e.g., cough, shortness of breath), AND with no other aetiology that fully explains the clinical presentation AND a history of travel to or residence in a country/area or territory reporting local transmission of COVID-19 disease during the 14 days before symptom onset. OR A patient with an acute respiratory illness AND having been in contact with a confirmed or probable COVID19 case (see definition of contact) in the last 14 days before the onset of symptoms; A patient with a severe acute respiratory infection (fever and at least one sign/symptom of respiratory disease (e.g., cough, shortness breath) AND requiring hospitalization AND with no other aetiology that fully explains the clinical presentation.
4. Probable cause: A suspect case for whom testing for COVID-19 is inconclusive. Inconclusive being the result of the test reported by the laboratory.
5. Confirmed case: A person with laboratory confirmation of COVID-19 infection, irrespective of clinical signs and symptoms.
6. Pandemic: A pandemic is a disease epidemic that has spread across a large region, for instance multiple continents, or worldwide.