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influenza
Definition of influenza
> The Italian word (influence) means a disease affected by weather conditions
A viral disease (RNA) of the orthomyxovirus family with three different types A, B, C with involvement of the respiratory system and a wide range of clinical symptoms, including asymptomatic cases to sudden onset of fever and dry cough, muscle pain, fatigue and lethargy, etc.
In children, it may have different manifestations, including higher fever and sometimes seizures, otitis media, croup, myositis, and pneumonia.
Gastrointestinal symptoms (vomiting and abdominal pain) are most common under 3 years of age
clinical features
human seasonal influenza
* fever high grade
* chills
* significant generalized ache and pain
* headache, myalgia
* coughing
* generalized weakness and exhaustion
fever last for 1+5 days and 3 days in adults
influenza & common cold
features influenza common cold
fever high uncommon
headache present uncommon
fatigue\weakness moderate mild
pain, ache moderate mild
exhaustion sever absent
stuffy nose &
sore throat uncommon common
cough present uncommon
Importance
> Creating widespread epidemics and pandemics
Creating death on a large scale
Impose a lot of costs
Complications
Influenza epidemics and pandemics
There are three influenza pandemics in the 20th century and one in the 21st century:
1. 1918 Pandemic (Spanish influenza): The most severe human pandemic with more than 40 million deaths even more than the killings of World War I and AIDS.
The disease originated from pigs to humans, the virus was influenza A (H1N1).
2 . 1957 pandemic (Asian influenza): with less pathogenicity than the previous pandemic due to less virus pathogenicity, global preparedness, provision of seasonal influenza vaccine, provision of antibiotics and formation of a global influenza surveillance system by WHO with the death of more than 1 million people
The epidemic origin of China and the virus resulting from the recombination of avian and human viruses H2N2
3. 1968 (Hong Kong Influenza) pandemic: milder than the previous pandemic with the death of about 1 million people, originating in southeastern China and spreading to Hong Kong, the recombinant virus of the avian and human viruses H3N2
4. 2009 Pandemic (Mexican Influenza):
The causative agent of virus A (H1NI), transmitted from pig to human. The estimated number of infected people is about 11-21% of the world’s population
Morbidity and high complications
نەخۆشی و ئاڵۆزییە بەرزەکان
> Pneumonia
Reye’s syndrome
Rhabdomyolysis
Myocarditis
Encephalitis
Guillain-Barre syndrome
Increasing death among high risk groups
Virological features
> The virus has three main types A, B, C.
Virus A is subdivided into different subtypes based on its surface glycoprotein type (both hemagglutinin HA and neuraminidase NA).
HA has 16 subtypes that only types 1, 2, and 3 are associated with widespread human pandemics.
HA causes agglutination of red blood cells and has the ability to bind and penetrate red blood cells.
NA is a fungal form and is responsible for releasing the virus from infected cells. So far, 9 subtypes have been identified, of which N1 and N2 are effective in human epidemics.
. Type B is associated with more limited epidemics, and type C is usually sporadic
Imposing costs on the community
سەپاندنی تێچوون بەسەر کۆمەڵگادا
Absence from work (payment of wages, reduction of production)
ئامادەنەبوون لە کار (دانی کرێ، کەمکردنەوەی بەرهەمهێنان)
Occupy hospital beds قەرەوێڵەی نەخۆشخانە داگیر بکە
Diagnostic costs and supply of medicine and treatment
تێچووی دەستنیشانکردن و دابینکردنی دەرمان و چارەسەرکردن
Costs of prevention and patient care
تێچووی خۆپاراستن و چاودێری نەخۆش
Education and research پەروەردە و توێژینەوە
Psychosocial injuries برینداربوونی دەروونی کۆمەڵایەتی
types of viruse
type A type B type C
causes causes only in
significant significant apparent
disease disease cases
epidemic & milder ——
pandemic epidemic
high morbidity& less morbidity& —–
mortality mortality
infect human & only human only human
other species
Antigenic antigenic antigenic
variations variations variations
frequently infrequent infrequent
Which antibodies against the flu virus play a major role in promoting immunity?
> Anti-H antigen antibody
Which antibodies play a major role in limiting the disease and preventing the spread of the disease?
Anti-N antigen antibody
Virus changes
> The most important feature of the influenza virus that is epidemiologically important.
These changes lead to the virus escaping the host’s immune response.
Shift: Occurs less frequently only in type A and creates a new subtype that can create a pandemic against which there is usually no immunity.
It is created by recombination between human and animal viruses, especially birds, or by direct transmission of a bird or swine virus to humans.
Drift: Common, followed by point mutations in HA and NA glycoproteins, followed by one or more amino acids in the virus structure, leading to new epidemics by viruses A and B and alteration of vaccines combinations.
So far, three types of hemagglutinin H1, H2, H3 and two types of neuraminidase N1, N2 have been identified in human influenza viruses.
History of virus A changes
> It was called H1N1 before 1957.
In 1957 there was a shift and H2N2 was formed (both H and N were changed).
In 1968 shifted again to form H3N2 (only H changed).
By 1978, eight major pandemics and epidemics had occurred.
Influenza types that circulate around the world include two types A and B and three subtypes H1N1 (pig), H3N2 and H5N1 (birds) of type A
Epidemiological factors
> Virus A infects a wide range of animals, birds, pigs, horses, dogs, cats and humans. The natural reservoir of these viruses is waterfowl.
Virus B has been identified in humans and hippopotamus.
Virus C has been isolated from humans, pigs and dogs.
Influenza epidemics occur in the cold seasons. Humidity and cold weather during the cold months lead to the retention of the virus in aerosols and respiratory droplets.
Survival of influenza virus in the environment: on plastic and steel more than 24 hours and on fabric, paper and tissue is between 8-12 hours.
> Methods of transmission: Direct contact of aerosols and respiratory droplets during sneezing and coughing or through contaminated objects and hands.
The incubation period is 1-5 days and the infectivity period is from 24 hours before the onset of symptoms until complete recovery.
The attack rate is 5-15%. Infection leads to incomplete immunity and re-infection occurs.
The main reasons for the rapid spread of influenza in society
> Short incubation period
. A large number of subclinical cases
Short immunity period
High number of sensitive population
Lack of cross immunity
The presence of the virus as latent infection between epidemics in the body of humans or animals
Diagnostic methods
> Using the swabs of the throat and nasopharynx in one of the following ways:
Isolation of the virus by cell culture in embryonic eggs (Gold Standard)
Serology (serum ELISA test for patients in the acute phase and recovery to determine antibodies) (only in research)
Rapid detection tests (low sensitivity and specificity)
RT-PCR (viral RNA) molecular detection tests (best early detection method)
