Causing Agent — Influenza occurs due to infection of respiratory tract by Influenza virus, RNA viruses of orthomyxovirus genus. There are four types of influenza virus designated as A, B, C and D. Influenza A and B occurs commonly in humans. It is responsible for outbreak of respiratory illness, mostly in winters. It also increases the chances of hospitalization and death. Influenza A can be further classified as hemagglutinin (HA) and neuraminidase (NA), on the basis of two surface proteins. Influenza A(H1N1), A(H3N2), and influenza B- Yamagata, B- Victoria viruses cocirculate in humans worldwide. The distribution of these viruses varies every year, according to the time and geographical areas. Avian and swine influenza viruses rarely infects humans, and is associated with close exposure to infected animal populations. Type C infection has no impact on public health. It may either cause mild respiratory infection or no symptom at all. Type D virus primarily affects cattle, and it is not known to cause any illness in human beings.
In what parts of the world this disease is found?
Influenza is more common in east than in west, especially in Southeast Asia. It is also found in America and Australia. Influenza A(H3N2) spreads around the world more quickly than H1N1 and influenza B. H3N2 strain mutates rapidly changing the key protein. Thus, people get flu every year, and they need vaccination to protect themselves from illness.
Scientists gathered the information by analyzing DNA from 10,000 flu viruses over 12 years and mapped them together, so that they can see how each strain spread quickly and what it means for virus evolution. The map below shows the spread of H3N2 virus. Color indicates the region and the size of bubble indicates size of the population. Bigger is the size of bubble, more is the virus.
Note: Some blank areas in the map does not mean that people of that area are not infected by the virus, it’s only the lack of data.
- H3N2 virus is the most common form of flu virus. Bedford et al.
- H3N2 virus goes around East and Southeast Asia, and spreads to rest of the world. H3N2 virus mutates quickly and spread among people of all ages, especially adults who travel and spread it around the world.
- H1N1 does not spread as quickly as H3N2. Bedford et al.
It is more common in children than adults, that is why it does not spread quickly because children travel less as compared to adults.
Means of Infection
Influenza virus can be transmitted in humans by direct contact with infected individuals, by contact with virus contaminated objects or surface, and by aerosol transmission.
The effect on the human body system
Influenza seems like a regular cold with a runny nose, sneezing and sore throat. Flu comes sudden whereas cold comes slowly and it can be a nuisance but flue makes you feel much worse.
Influenza virus can be detected in body if all these following symptoms can be seen in humans : Fever over 100.4 F (38 degree C), cough, chest discomfort (dry cough can be severe), Fatigue and weakness, Nasal congestion, chills and sweats, body aches and pains (can be severe), Aching muscles, bedridden ( you may feel extremely exhausted), Headache (can be severe), sore throat, stuffy, runny nose. There are some risk factors that increases the risk of getting influenza are Age, living and working condition, weakened immune system chronic illness, Aspirin use under the age of 19, pregnancy, obesity. People living and working in facilities with many other residents, such as nursing homes or military barracks and people who are hospitalized are at the high risk of getting influenza.
Part of the body the disease affects
Influenza virus has an effect on the human body system as following: causing lungs infection, throat infection, ear infection and sinus infections. Influenza is a viral infection that mainly attacks respiratory system that includes nose, throat and lungs. High risk of serious complications can be seen in people with age group 65 or above, young children under age 5 and especially those under 12 months, pregnant women and women up to two weeks postpartum, indegenous people, those living with one or more chronic health conditions such as asthma, heart disease, kidney disease, liver disease and diabetes and those residing in nursing homes or other facilities and people with weak immune sustem and who are very obese, with a body mass index of 40 or higher.
Preventions- flu virus change itself every year. Vaccines for viruses are created every year by the experts. To prevent flu virus every person should get vaccinated every year. The viruses in the Flu shot are either killed or weakened and cannot give you the flu.
- Public Health Agency of Canada. (2018, October 19). Government of Canada. Retrieved from https://www.canada.ca/en/public-health/services/diseases/flu-influenza.html.
- Potter, C. W. (2008, July 7). A history of influenza. Retrieved from https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2672.2001.01492.x.