Spanish flu Pandemic
1918-1919 pandemic caused ~ 50 million deaths worldwide. This pandemic spread simultaneously in 3 distinct waves within 12 moths in Europe, Asia and North america.
The first pandemic wave happened during spring and summer of 1918, it appeared as mild flu. The second wave appeared with severe flu symptoms in the fall of 1918. The third wave happened during spring of 1919 and was much more fatal than the first 2 waves.
The Spanish flu was originally given its name because it was believed that the disease originated in Spain. The truth however is likely more political than that. During World War 1 (when the Spanish flu was predominant ) many countries censored the true number of Spanish flu deaths an an effort to keep soldier’s morale high. Spain however, was neutral in their reporting of the number of deaths from the Spanish flu, which created the illusion that the disease was predominant in Spain.
Although the flu didn’t actually originate in Spain, the first reports of the flu did originate from Spain. at the time, Spanish media was more transparent about the disease, and the first reports of the outbreak came from Spain. It is not known where exactly the disease originated from, bit many believe that the disease originated on battlefields somewhere in Europe or the united states.
Because Spanish flu is not the name of an actual disease, but rather the name given to the pandemic, you would not find Spanish flu at other points in history. However, the H1N1 virus (that caused Spanish flu), and other similar viruses have seen outbreaks throughout history. The most recent example of H1N1 virus that has been seen occurred in 2009. In 2005, the H1N1 virus also saw an outbreak.
What is H1N1 ?
Influenza H1N1 is a subset of the Influenza A virus. Two of the most notable cases of H1N1 influenza are Spanish flu and the 2009 swine flu outbreak. Though both of these cases of influenza were caused by the H1N1 virus, the origin of the virus was birds in the Spanish flu, and swine in the 2009 influenza outbreak.
H1N1 influenza is a negative strand RNA viruses “orthomyxovirus” compromised of the glycoproteins haemagglutinin (H) and neuraminidase (N). The numbering in the name originated from what antigens each glycoprotein expresses.
The H1N1 virus causes respiratory issues, and it is very contagious.
Data of viral sequence suggest the virus produced from old existing strains but acquired 1 or more new genes, 1918 virus looks like avian influenza virus.
This pandemic was associated with the emergence of antigenic shifts in both the hemagglutinin (H1) and the neuraminidase (N1) of influenza A .
Hemagglutinin (H) antigen binds to receptors and fuses to host cell membranes. There are 15 known H antigens, only H1, H2, and H3 are known to infect humans.
Neuraminidase (N) antigen cleaves budding viruses from infected cells. There are 9 known N antigens, only N1 and N2 are known to infect humans.
Antigenic shift occur by 2 different mechanism. The first mechanism called Genetic Reassortment that occurs when pieces of both influenza viruses become mixed into a viron, resulting in a new strain of influenza . The second mechanism called Adaptive Mutation when the virus adjusts and becomes transmissible which Results in a novel virus “against which there is little to no pre-existing immunity” and This increases new risks for pandemics.
H1N1 Pathogenesis :
The HA protein on the surface of the virus bind to sialic acid receptor on the host cell and this allow the entry of the virus. Ciliated columnar epithelium like alveolar cell and mucus gland cell are the most common infected cell with this virus. After the entry, the virus start to replicate and form new viral particle that spread to other cell but it it’s rarely spread to lower respiratory tract, blood stream and extra pulmonary sites.
The virus lead to local damage by cellular destruction, desquamation, edema, mononuclear cell infiltration and cytokine influx. Secondary bacterial invasion like staphylococci , pneumococci and H. influenza can happen and lead to pneumonia.
H1N1 Transmission :
The Spanish flu was spread by droplets. some common ways that droplet are spread are sneezing, coughing, talking and yelling.
Because the Spanish flu was extremely predominant in world war 1 battlefields, the close proximity of soldiers is likely one of the factors that resulted in the significant spread of the illness. Poor hygiene was also a culprit in the spread of Spanish flu. During WW1 hygiene on the battlefield was often less than adequate. In some cases, soldiers would develop both the viral Spanish flu as well as a bacterial infection resulting in super infection.
Another significant factor in the spread of the Spanish flu was accessibility of travel. Cars, trains and more advanced water travel allowed the infected patient to spread the disease across the world.
Presentation of Spanish flu :
symptoms of Spanish flu are similar to the symptoms of regular influenza A. some symptoms are :
- Shortness of breath
- Coughing of bloody sputum
Mortality rates were the highest in younger age group ( younger than 5 years old , 20-40 years old and 65 years and older). Mortality rate varied in different area of the world, with fatality rate between 2.5 and 5% of the people on earth at that time.
Sickness lasted 5 days before patients were killed from a viral pneumonia (developed in 10%- 20% pf cases) accompanied by a massive acute pulmonary hemorrhage or pulmonary edema.
Spanish flu Treatment :
Treatment options were very limited at that time. The best option was to use preventative measures. The local health stores distributed gauze masks and encourage social distancing and quarantining infected people.
The Spanish flu pandemic ended when patient infected bacame immune to it .
Today the Spanish flu is no longer a threat because vaccines have been made and testing has been invented.