Seasoal Influenza Viruses pptx - D. Muslim

Control of communicable diseasesRespiratory diseasesStage 4-L7

Influenza viruses
By Dr. Muslim N. Saeed \ FAMCO dept.
February 25th, 2020

Influenza

-Highly infectious viral illness
-First pandemic in 1580
-At least 4 pandemics in 19th century
-Estimated 21 million deaths worldwide in pandemic of 1918-1919
-Virus first isolated in 1933

Influenza Virus-Single-stranded RNA virus Orthomyxoviridae family -3 types: A, B, C -Subtypes of type A determined by hem-agglutinin and neuraminidase

Influenza A causes moderate to severe illness and affects all age groups. The virus infects humans and other animals. Influenza A viruses are perpetuated in nature by wild birds, predominantly waterfowl.
Most of these viruses are not pathogenic to their natural hosts and do not change or evolve.

Influenza B generally causes milder disease than type A and primarily affects children. Influenza B is more stable than influenza A, with less antigenic drift and consequent immunologic stability. It affects only humans.
Influenza C is rarely reported as a cause of human illness, probably because most cases are subclinical. It has not been associated with epidemic disease.

Antigenic Changes

Hemagglutinin and neuraminidase periodically change, apparently due to sequential evolution within immune or partially immune populations.
Influenza Antigenic Changes
1-Antigenic Drift
-minor change, same subtype
-caused by point mutations in gene
-may result in epidemic
2-Antigenic Shift
-major change, new subtype
-caused by exchange of gene segments
-may result in pandemic

2009 Influenza A(H1N1)

-In April 2009 a novel influenza A(H1N1) virus appeared and quickly spread across North America.
-By May 2009 the virus had spread to many areas of the world cause of the first influenza pandemic since 1968
-Pandemic monovalent influenza vaccine produced and deployed in nationwide vaccination campaign.

Viral Re-assortment

Reassortment in pigs

Reassortment in humans

Pandemic Influenza Virus

Influenza Pathogenesis

-Respiratory transmission of virus
-Replication in respiratory epithelium
-destruction of cells
-Viremia rarely documented
-Virus shed in respiratory secretions for 5-10 days

Clinical Features

The incubation period for influenza is usually 2 days, but can vary from 1 to 4 days. Influenza illness can vary from asymptomatic infection to severe. In general, only about 50% of infected persons will develop the classic clinical symptoms of influenza.

“Classic” influenza disease is characterized by the abrupt onset of fever, myalgia, sore throat, nonproductive cough, and headache.
Myalgias mainly affect the back muscles.
Additional symptoms may include rhinorrhea (runny nose), headache, substernal chest burning and ocular symptoms (e.g., eye pain and sensitivity to light).
Systemic symptoms and fever usually last from 2 to 3 days, rarely more than 5 days.
-Aspirin should not be used for infants, children, or teenagers because they may be at risk for contracting Reye syndrome following an influenza infection.

Influenza Complications

1-Pneumonia secondary bacterial or primary influenza viral.
2-Reye syndrome
3-Myocarditis
4-Death is reported than less than 1 per 1,000 cases

Influenza Diagnosis

-Clinical and epidemiological characteristics
-Isolation of influenza virus from clinical specimen (e.g., throat, nasopharynx, sputum)
-Significant rise in influenza IgG by serologic assay

Epidemiology

Occurrence
Influenza occurs throughout the world.
Reservoir
Humans are the only known reservoir of influenza types B and C. Influenza A viruses may infect both humans and animals. There is no chronic carrier state.
Transmission
-Influenza is primarily transmitted from person to person via large droplets (particles more than 5 microns in diameter) that are generated when infected persons cough or sneeze.

-Transmission may also occur through direct contact or indirect contact with respiratory secretions such as when touching surfaces contaminated with influenza virus and then touching the eyes, nose or mouth.
Temporal Pattern
-Influenza activity peaks from December to March in temperate climates, but may occur earlier or later.
-Influenza occurs throughout the year in tropical areas.
Communicability
Adults can transmit influenza from the day before symptom onset to approximately 5 days after symptoms begin. Children can transmit influenza to others for 10 or more days.

Prevention and control

Influenza Vaccines
1-Inactivated subunit (IIV) intramuscular or intra-dermal (available in Iraq).
2-Live attenuated vaccine (LAIV) (intranasal).

Inactivated Influenza Vaccine Recommendations

When vaccine supply is limited, vaccination efforts should focus on delivering vaccination to the following groups of persons:
1-Children 6 months through 4 years (59 months) of age
2-persons 50 years and older
3-persons with chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus)
4-persons who are immunosuppressed (including immunosuppression caused by medications or by human immunodeficiency virus)
5-women who are or will be pregnant during the influenza season

6-children 6 months through 18 years of age and receiving long-term aspirin therapy(Reye syndrome risk after influenza virus infection).
7-Residents of nursing homes and other chronic-care facilities.
8-Persons who are morbidly obese (body-mass index is 40 or greater) .
9-Healthcare personnel
10-Household contacts and caregivers of children younger than 5 years of age and adults 50 years of age or older.
11-Household contacts and caregivers of persons with medical conditions that put them at higher risk for severe complications from influenza.

Pregnancy and Inactivated Influenza Vaccine
-Risk of hospitalization 4 times higher than non pregnant women
-Risk of complications is higher comparable to non-pregnant women.
-Vaccination (with IIV) recommended if pregnant during influenza season.
-Vaccination can occur during any trimester

Inactivated Influenza Vaccine Contraindications and Precautions

1-Severe allergic reaction (e.g., anaphylaxis) to a vaccine component or following a prior dose of inactivated influenza.
2-Moderate or severe acute illness
3-History of Guillain-Barré syndrome (GBS).

Influenza Antiviral Agents

-Amantadine and Rimantadine not recommended because of documented resistance.
-Zanamivir and oseltamivir are neuraminidase inhibitors are effective against influenza A and B .
-oseltamavir and zanamavir approved for prophylaxis.

Antivirals- Oseltamivir

• -Treatment is 75 mg twice a day for 5 days.
• -Prophylaxis is 75 mg once a day for 7 days after last exposure.
• -Prophylaxis:
• 1.High risk exposure (household contacts)
• 2.Moderate risk (unprotected very close exposure to sick animals; Health Care Workers with unprotected exposure to patients).
• 3.Low risk exposure: no need for prophylaxis.

Cough etiquette
Respiratory etiquette
-Cover nose / mouth when coughing or sneezing
-Hand washing.

Voluntary Isolation

-Separation and restricted movement of ill persons with contagious disease (often in a hospital setting and Primarily individual level)
-Isolate severe and mild cases
-Location of isolation (home, hospital) depends on several factors (severity of illness, the number of affected persons, the domestic setting)
-Do not wait for lab confirmation
-Plan for large number of severe cases
-Provide medical and social care

Voluntary Quarantine

1-Separation and restricted movement of well persons presumed exposed
2-Identification of contacts
-Often at home, but may be designated residential facility or hospital
-Applied at the individual or community level
3-Regular health monitoring is essential part of quarantine
-Self-health monitoring and reporting

Patients Care at Home
-Potential for transmission
-Must educate family caregivers
-Fever / symptom monitoring
-Infection control measures
Hand washing
Use of available material as mask …