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Influenza infection
This document discusses influenza infection. It describes influenza viruses as RNA viruses in the orthomyxovirus family that are 80-200nm in diameter. There are three main types - A, B, and C - which are further classified into subtypes based on surface proteins. The document defines terms like epidemic, pandemic, antigenic drift, and antigenic shift. It also outlines the normal disease burden of seasonal influenza, symptoms of influenza, recommendations for prevention and control, and guidelines for vaccination from the Advisory Committee on Immunization Practices.
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Influenza infection
- 1. INFLUENZA INFECTIONINFLUENZA INFECTION ByM Osama Hussein. MD
- 2. Credit: L. Stammard,1995 • RNA, enveloped • Viral family: Orthomyxoviridae • Size: 80-200nm or .08 – 0.12 μm (micron) in diameter • Three types • A, B, C • Surface antigens • H (haemaglutinin) • N (neuraminidase) Influenza VirusInfluenza Virus
- 3. H1 N1 H2 N2 H3N3 H4 N4 H5 N5 H6 N6 H7 N7 H8 N8 H9 N9 H10 H11 H12 H13 H14 H15 H16 Haemagglutinin subtype Neuraminidase subtype
- 5. EpidemicEpidemic – alocated cluster of cases– a located cluster of cases PandemicPandemic – worldwide epidemic– worldwide epidemic Antigenic driftAntigenic drift ◦ Changes in proteins by genetic point mutation &Changes in proteins by genetic point mutation & selectionselection ◦ Ongoing and basis for change in vaccine each yearOngoing and basis for change in vaccine each year Antigenic shiftAntigenic shift ◦ Changes in proteins through genetic reassortmentChanges in proteins through genetic reassortment ◦ Produces different viruses not covered by annualProduces different viruses not covered by annual vaccinevaccine DefinitionsDefinitions
- 6. InfluenzaInfluenza The Normal Burdenof DiseaseThe Normal Burden of Disease Seasonal Influenza ◦ Globally: 250,000 to 500,000 deaths per year ◦ In the US (per year) ~35,000 deaths >200,000 Hospitalizations $37.5 billion in economic cost (influenza & pneumonia) >$10 billion in lost productivity Pandemic Influenza ◦ An ever present threat
- 7. Reassortment in Pigs SwineInfluenza A(H1N1)Swine Influenza A(H1N1) Transmission Through SpeciesTransmission Through Species
- 8. Swine Influenza A(H1N1)SwineInfluenza A(H1N1) Global ResponseGlobal Response Source: WHO
- 9.
- 11. Influenza Symptoms Influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly.
- 12. Influenza SymptomsInfluenza Symptoms Fever* or feeling feverish/chills Cough Sore throat Runny or stuffy nose Muscle or body aches Headaches Fatigue (tiredness) Vomiting and diarrhea, children
- 15. Swine Influenza A(H1N1)SwineInfluenza A(H1N1) Guidelines for General PopulationGuidelines for General Population Covering nose and mouth with a tissue when coughing or sneezing ◦ Dispose the tissue in the trash after use. Handwashing with soap and water ◦ Especially after coughing or sneezing. Cleaning hands with alcohol-based hand cleaners Avoiding close contact with sick people Avoiding touching eyes, nose or mouth with unwashed hands If sick with influenza, staying home from work or school and limit contact with others to keep from infecting them
- 16. Recommendations for Preventionand ControlRecommendations for Prevention and Control of Influenza in Children, 2016–2017of Influenza in Children, 2016–2017 COMMITTEE ON INFECTIOUS DISEASESCOMMITTEE ON INFECTIOUS DISEASES Pediatrics September 2016 From the American Academy of Pediatrics Policy Statement
- 17. 1. Annual universalinfluenza immunization is indicated with either a trivalent or quadrivalent (no preference) inactivated vaccine.
- 18. 2. The 2016–2017influenza A (H3N2) vaccine strain differs from that contained in the 2015– 2016 seasonal vaccines. The 2016–2017 influenza B vaccine strain (Victoria lineage) included in the trivalent vaccine differs from that contained in the 2015–2016 seasonal trivalent vaccines (Yamagata lineage).
- 19. 3. Quadrivalent liveattenuated influenza vaccine (LAIV4) should not be used in any setting during the 2016–2017 influenza season in light of the evidence for poor effectiveness of LAIV4 in recent seasons, particularly against influenza A (H1N1)pdm09 viruses.
- 20. 4. All childrenwith egg allergy can receive influenza vaccine with no additional precautions from those of routine vaccinations.
- 21. 5. All HCPshould receive an annual influenza vaccine, a crucial step in preventing influenza and reducing health care–associated influenza infections. Because HCP may care for or live with people at high risk of influenza-related complications, it is especially important for them to get vaccinated annually.
- 22. 6. Pediatricians shouldattempt to promptly identify children suspected of having influenza for rapid antiviral treatment, when indicated, to reduce morbidity and mortality.
- 25. Prevention andControl of Seasonal Influenza with Vaccines Recommendations of the Advisory Committee on Immunization Practices — United States, 2016–17 Influenza Season August 26, 2016 / Grohskopf, et al Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications.
- 26. live attenuatedinfluenza vaccine (LAIV4) should not be used. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is otherwise appropriate.
Editor's Notes
- #3 The internal antigens (M1 and NP proteins) are the type-specific proteins (type-specific antigens) used to determine if a particular virus is A, B or C. The M1 proteins of all members of each type show cross reactivity. The NP proteins of all members of each type also show cross reactivity. The external antigens (HA and NA) show more variation and are the subtype and strain-specific antigens. These are used to determine the particular strain of influenza A responsible for an outbreak Flu strains are named after their types of hemagglutinin and neuraminidase surface proteins, so they will be called, for example, H3N2 for type-3 hemagglutinin and type-2 neuraminidase. If two different strains of influenza infect the same cell simultaneously, their protein capsids and lipid envelopes are removed, exposing their RNA, which is then transcribed to mRNA. The host cell then forms new viruses that combine antigens; for example, H3N2 and H5N1 can form H5N2 this way. Because the human immune system has difficulty recognizing the new influenza strain, it may be highly dangerous.
- #4 Influenza A viruses are found in many different animals, including ducks, chickens, pigs, whales, horses, and seals. There are 16 different haemaglutinin subtypes and 9 different neuraminidase subtypes, all of which have been found among influenza A viruses in wild birds. Wild birds are the primary natural reservoir for all subtypes of influenza A viruses and are thought to be the source of influenza A viruses in all other animals. Most influenza viruses cause asymptomatic or mild infection in birds; however, the range of symptoms in birds varies greatly depending on the strain of virus. Infection with certain avian influenza A viruses (for example, some strains of H5 and H7 viruses) can cause widespread disease and death among some species of wild and especially domestic birds such as chickens and turkeys. Pigs can be infected with both human and avian influenza viruses in addition to swine influenza viruses. Infected pigs get symptoms similar to humans, such as cough, fever, and runny nose. Because pigs are susceptible to avian, human and swine influenza viruses, they potentially may be infected with influenza viruses from different species (e.g., ducks and humans) at the same time. If this happens, it is possible for the genes of these viruses to mix and create a new virus.
- #8 Reassortment, or Viral Subunit Reassortment, is the exchange of DNA between viruses inside a host cell. Two or more viruses of different strains (but usually the same species) infect a single cell and pool their genetic material creating numerous genetically diverse progeny viruses. It is a type of genetic recombination. Reassortment can lead to a viral shifts under some conditions.
- #9 WHO Definition of Phases Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion. Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short. Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way. During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave. Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature. In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.