Influenza by dr najeeb

By : DR: NAJEEB MEMON Assist: ProfessorFaculty of community Medicine & Public Health SciencesLiaquat University of Medical & Health Sciences (LUMHS)JAMSHORO SIND PAKISTAN : 

By : DR: NAJEEB MEMON Assist: ProfessorFaculty of community Medicine & Public Health SciencesLiaquat University of Medical & Health Sciences (LUMHS)JAMSHORO SIND PAKISTAN e mail mnajeeb80@gmail.com

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INFLUENZA

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common cold / acute coryza / acute viral rhino pharyngitis & flu are both respiratory illnesses, but they are caused by different viruses. A cold virus usually infects only your upper respiratory tract: your nose and throat. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations. Rhinovirus adenoviruses, corona viruses Influenza or "the flu" develops when a flu virus infects your respiratory system, including your nose, throat, bronchial tubes, and possibly the lungs. Flu symptoms are generally worse than illness caused by the common cold. Ortho myxoviruses common cold / acute coryza Influenza or " Flu"

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Stuffy nose may mean cold

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Fatigue in Flu

Influenza virus Types : 

Influenza virus Types type A type B type C human sporadic cases mild AURI, no epidemic human , Pigs, birds, chickens & Horses primary pathogen mild – severe AURI & ALRI epidemic, potently pandemic human primary pathogen mild - moderate AURI, epidemic Nelson 18th ed, 2007 Avian Influenza most common strain of virus. outbreaks also can cause epidemics ( Milder than A ) Never connected with a large epidemic.

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Subtypes Of A virus The hemagglutinin of the 1918 flu virus was H1, its neuraminidase was N1, so it is designated as an H1N1 "subtype". Flu pandemics occur when the virus acquires a new hemagglutinin and/or neuraminidase.

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Influenza A viruses also infect domestic animals (pigs, horses, chickens, ducks) and some wild birds.

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TYPE A ++++ yes yes yes shift, drift yes sensitive sensitive 2 severity of illness animal reservoir human pandemics human epidemics antigenic changes segmented genome amantadine, rimantidine zanamivir surface glycoproteins TYPE B ++ no no yes drift yes no effect sensitive 2 TYPE C + no no no (sporadic) drift yes no effect (1)

Types of Flu : 

Types of Flu Hong Kong influenza - H3N2 strain of Influenza A in 1968 Russian influenza - a 1978 epidemic. Spanish influenza - H1N1 1918. & 2009 flu pandemic Asian influenza - H2N2 a strain of Influenza A , in 1957. Swine flu hog flu, pig flu - an epidemic in 1976, in the United States Avian flu - a chicken flu in Hong Kong in 1997 •H5N1, a current pandemic threat Bird flu •H7N7, which has unusual zoonotic potential •H1N2, endemic in humans and pigs •H9N2 •H7N2 •H7N3 •H10N7 Most major pandemics have been caused by the A type – H5(bird flu), H1N1 (swine flu) , as also H2N2, H3N2, etc.

Influenza - epidemiology : 

Influenza - epidemiology Although influenza affects people of all ages, the highest morbidity and mortality occur in infants. The attack rate is highest among school-aged children Epidemics of influenza occur during winter months. Transmission by aerosol droplets as well as by direct or indirect contact. Complication rates increase in children <2 years old and those with high-risk conditions.

Influenza - risk factors : 

Influenza - risk factors High risk conditions for severe disease include: Chronic pulmonary disease (i.e., asthma), hemodynamically significant cardiac disease, HIV and other immunodeficiencies, chronic immunosuppressive therapy, hemoglobinopathies (i.e., sickle cell disease), long-term salicylate use, chronic renal dysfunction, and chronic metabolic disease.

Influenza - etiology : 

Influenza - etiology The orthomyxo viruses influenza types A, B, and C. Influenza A has subtypes defined by 2 surface antigens: Hemagluttinin and Neuraminidase

Hemagluttinin and neuraminidase : 

Hemagluttinin and neuraminidase

Problem statement : 

Problem statement It may occur in pandemics every 10-15 years due to major antigenic changes, as occurred in 1957 and 1968. In between pandemics, epidemics tend to occur at intervals of 2-3 years in case of influenza A and 4-7 years in the case of influenza B- out breaks of influenza practically every year, and sometimes even twice a year.

Agent Factors : 

Agent Factors AGENT: Family Orthomuxoviridae type A, B and C are antigenic ally distinct. A and B viruses responsible for epidemics A & B viruses have 2 distinct surface antigens – haemagglutinin (H) ( attachment of the virus to susceptible cells.) neuraminidase (N) antigens. ( release of the virus from the infected cell.)

Antigenic Shift / Drift : 

Antigenic Shift / Drift When there is a sudden complete or major change, it is called a shift. when the antigenic change is gradual over a period of time, it is called a drift. Antigenic DRIFT: yearly epidemics Antigenic SHIFT: Influenza pandemic (every 10-40 years)‏

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The influenza A virus can mutate in two different ways; antigenic drift, in which existing antigens are subtly altered, and antigenic shift, in which two or more strains combine. Antigenic drift causes slight flu mutations year on year, from which humans have partial, but not complete, immunity. By contrast, the new strain of H1N1 appears to have originated via antigenic shift in Mexican pigs.

RESERVOIR OF INFECTION: : 

RESERVOIR OF INFECTION: In animals and birds. E. g:- swine, horses, dogs, cats, domestic, poultry, wild birds, etc some of these include the major H and N antigens related to human strains.

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SOURCE OF INFECTIVITY: Secretions of the respiratory tract are infective. PERIOD OF INECTION: Virus is present in the nasopharynx from 1-2 days before and 1-2 days after onset symptoms.

Host factors : 

Host factors AGE & SEX: Affects all ages and both sexes. Children constitute an important link in the transmission chain. Old people children under 18 months, with diabetes or chronic heart disease, kidney respiratory. HUMAN MOBILITY: IMMUNITY: Antibodies are important in immunity against influenza.

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Environmental factors. Season: Winter months, rainy season. In India Summer. Over crowding : Enhances transmission, close population groups, schools, institutions, ships, etc. Mode of transmission Infection, droplet nuclei, sneezing, coughing, talking, respiratory tract. Incubation period: 18-72 hours.

Clinical features : 

Clinical features Fever, chills, pains. Coughing, generalized weakness. Fever lasts from 1-5 days, complication is pneumonia.

Laboratory diagnosis : 

Laboratory diagnosis VIRUS ISOLATION: Nasopharyngeal secretions, by the indirect fluorescent antibody technique, egg inoculation is required for virus isolation, antigenic analysis. PAIRED SERA specimens.

Influenza - testsInfluenza - lab : 

Influenza - testsInfluenza - lab Viral culture from nasopharyngeal secretions will be positive within 2–6 days. Direct immunofluorescent antibody (DFA) and indirect immunofluorescence antibody (IFA) tests. Rapid antigen testing RAT is available for diagnosing influenza A and influenza B. Enzyme-linked immunosorbent assay ELISA for influenza

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To Prevent H1N1 Spreading or Contracting? Good Personal Hygiene-habits via Hand-Washing/Cleansing with soap or with Alcohol-based sanitizers Environmental Hygiene Ensuring regular cleaning and sterilizing of work areas or Equipments avoidance of crowded places Covering of mouth for coughs & sneezing Stay at home Masks / Gowns when unwell Monitoring Temperature Maintaining a Healthy Lifestyle Exercising Consuming a Balanced Diet and adequate amount of Water daily Essential Supplements such as Vitamins A, C, E, and Zinc Adequate rest Avoid those who are ill Yearly Influenza shot Antiviral in special circumstances.

Influenza vaccines : 

Influenza vaccines Flu vaccines first produced in 1940s KILLED VACCINES LIVE ATTENUATED VACCINES NEWER VACCINES NEURAMINIDASE SPECIFIC VACCINE containing only the N antigen, which includes antibodies only to the neuraminidase antigen of the prevailing influenza virus RECOMBINAT VACCINE

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Recommendation For Seasonal Influenza Vaccination Who should be vaccinated? Travelers Children 6 months – 5 years Elderly > 65 Residents of nursing homes People with long term-illnesses (e.g. heart/lung)‏ People with depressed immunity Pregnant women in 2nd-3rd trimester Healthcare workers EVERYONE in the face of a Pandemic-threat

Antiviral drugs : 

Antiviral drugs For the prophylaxis and therapy of influenza type A infections Amantadine Rimantidine. How ever, these drugs have not been used as a public health measures for the widespread control of influenza A.

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Swine influenza

Swine influenza : 

Swine influenza

Swine influenza / swine flu/ hog flu, pig flu /and sometimes, the swine : 

Swine influenza / swine flu/ hog flu, pig flu /and sometimes, the swine infection by any one of several types of swine influenza virus. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3.

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Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. The meat of an infected animal poses no risk of infection when properly cooked. These strains of swine flu rarely pass from human to human. Symptoms of zoonotic swine flu in humans are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. The recommended time of isolation is about 5 days

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The name "swine flu" is a slight misnomer as it is believed pigs acted as a mixing pot for several flu strains, containing genetic material from pigs, birds and humans. Most humans have never been exposed to some of the antigens involved in the new strain of flu, giving it the potential to cause a pandemic.

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The new virus has made the jump from pigs to humans and has demonstrated it can also pass from human to human. This is why it is demanding so much attention from health authorities. The virus passes from human to human like other types of flu, either through coughing, sneezing, or by touching infected surfaces, although little is known about how the virus acts on humans

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Bron: NPR. Confirmed Cases Of Swine Flu Across The Globe.

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Avian influenza, or “bird flu” BIRD FLU

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Avian influenza, or “bird flu”, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans. Avian influenza, or “bird flu”

Bird Flu : 

Bird Flu

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For example: pigs simultaneously infected with swine flu virus (H1N1) and the Hong Kong virus (H3N2): H3 and N1 are reassorted in a pig and a new H3N1 virus appears. Reassortment can also occur in humans with dual infections.

Comparison : 

Comparison

High risk for complications : 

High risk for complications Children less than 5 years old; Persons aged 50 years or older; Children and adolescents (<18 yrs) who are receiving long-term aspirin therapy Pregnant women; Patients who have chronic medical conditions; Patients in immunosuppression conditions Residents of nursing homes and other chronic-care facilities. CDC 2009, Guidance on identifying & caring