Influenza

Identification: Acute viral respiratory infection, characterized by systemic manifestations- fever, rigors, headache, malaise & muscle pains. With local manifestations- of coryza, sore throat and severe protracted cough. The important complication is secondary bacterial pneumonia, Reye syndrome (in children).

Severe illness and death during annual influenza epidemics (seasonal influenza) occur primarily among elderly (80-90% of deaths occur in persons over 65 yrs) and those debilitated by chronic illnesses.

2. Infectious agent: Influenza Virus Types A, B & C according to antigenic properties of 2 internal structure proteins: nucleo protein & matrix protein. Type A usually associated with widespread epidemics (seasonal flu) & pandemics (pandemic flu). Type B is infrequently associated with regional or widespread epidemics (seasonal flu). Type C is associated with sporadic and minor localized outbreaks.

Type A: Subtypes: depend on surface Ag which are; haemagglutinin H (H1, H2, H3) &Neuraminidase N (N1, N2) Ag Influenza A include 3 subtypes {H1N1, H2N2, H3N2}. That are described by geographical site of isolation, year of isolation and culture no. Examples: Type / site origin / no. / year isolation / subtype A / Johannesburg / 33 / 94 / (H3N2) B / Hong Kong / 330 / 2001

Antigenic variation Antigenic shift: Emergence of completely new virus subtypes- at irregular intervals and only for type A viruses- result from antigenic shift in HA gene or unpredictable recombination of human and mammalian or avian antigens (swine and some wild and domestic fowl) and lead to pandemics. Type B has no animal reservoir → no antigenic shift. Antigenic drift: The relatively minor antigenic changes or spontaneous mutation (antigenic drift) of A & B viruses responsible for frequent epidemics and regional outbreaks which occur constantly (annually) and require annual reformulation of influenza vaccine.

Pandemics (rare) -type A. Occurrence: Pandemics (rare) -type A. Epidemics ( almost annual)-type A, B or both. Localized out breaks and sporadic cases (every year) –type C. Pandemics of influenza: is the emergence of the disease among humans by new subtype of influenza viruses with new surface proteins, and ranking as global health emergencies, here children and adults are equally susceptible. e.g. 1889, 1918, 1957, 1968, 2009 with millions of deaths (50 – 100 millions in Spanish pandemic 1918).

Influenza epidemic (seasonal flu): Attack rate during epidemics 10-20% in the general community to more than 50 % in closed community (schools). Epidemics generally last 3-6 weeks, usually in winter, while outbreaks or sporadic cases may occur in any month. In epidemics populations partially protected because of earlier infections.

Modes of transmission: Reservoir: -Human are the primary one in the human infections. Modes of transmission: Airborne spread among crowded populations in enclosed spaces. - Direct contacts. - Handling of contaminated articles. I.P: 1-3 days. Period of communicability: 3-5 days from clinical onset (adult). Up to 7 days in young children.

Susceptibility & resistance Infection produces immunity to the specific antigenic variant of the infecting virus, and the duration of immunity depend on the degree of antigenic similarity between viruses causing immunity. Pandemics (emergence of new subtype) → all susceptible.

2 doses one month apart, repeated annually Methods of control: Preventive measures: H.E to the public about personal hygiene to avoid unprotected cough and sneezes, overcrowding etc. Inactivated influenza vaccines (killed) derived from A and B viruses that circulated during previous season, 70-90% protection. Given at autumn & repeated annually (routinely given for those risky groups). It may cause low grade fever and redness. 2 doses one month apart, repeated annually Recently: live attenuated trivalent vaccine A Given intranasal, promising results 3. Chemoprophylaxis (Anti-viral drugs)

Indication of vaccine: Healthy individuals >65 years (the vaccine less effective in preventing infection but: ↓ severity, ↓ complications, ↓ death by 80%) Individual needs regular medical attention e.g. DM, renal failure, haemoglobinopathies and immunosuppresed. Individual provides care to those at high risk including close contacts and health staff. Children on long term use of aspirin to avoid Reye's syndrome.

3. chemoprophylaxis of type A Amantadine or rimantadine. Same indications as vaccine. Chemoprophylaxis used when vaccine not available or as a supplement to vaccine when immediate maximal protection is desired against type A.

B) Control of pts, contacts and environment: Reporting: Only for outbreaks. Isolation: Impractical because of delay Dx. Quarantine: Not Applicable. Protection of contacts: by chemoprophylaxis. Specific Rx: Amantadine or rimantadine 100 mg twice daily, within 48 hrs of onset of illness and for 3-5 days can reduce symptoms and virus titer in respiratory secretion. - Rx of secondary bacterial infections. - Avoid salicylates in children.

Pandemic flu 2009 “H1N1” (Swine flu Or Pig flu) Introduction : It is a highly contagious respiratory disease in pigs. Caused by several swine influenza A virus (H1N1). Transmission of virus from pigs to human is not common. People with regular contact to infected pigs increase risk of infection then after human to human transmission could occur.

- June 11, 2009 WHO declared onset of influenza pandemic. History : Swine influenza was first proposed to be a disease related to human influenza during 1918. 1976 U.S. out break in New-jersey, more than 200 cases with 1 death (soldier). The vaccine program was started on October 1, 1976, (GBS of 3 cases but not proved). Another out breaks in 1988, 1998 (US). 2009 out break in Human : - June 11, 2009 WHO declared onset of influenza pandemic. Globally: CRF 0.02 %. The most common cause of death is respiratory failure.

Up date estimate of CD from April 2009 through February 13, 2010 on March 12, 2010 Estimated range Mid level range 2009 H1N1 ~14 – 28 million ~24 – 50 million ~ 4 - 8 million ~42 – 86 million ~19 million ~34 million ~6 million ~59 million Cases 0 – 17 y. 18 – 64 y. 65 y. & older Cases total 60 000 – 125 000 109 000 – 226 000 19 000 – 38 000 188 000 – 389 000 ~ 85 000 ~154 000 ~26 000 ~265 000 Hospitalization Hosp. total 890 – 1 840 6 530 – 13 500 1 100 – 2 280 8 520 – 17 620 ~1 250 ~9 200 ~1 550 ~12 000 Death Death total

Reservoir : swine. Mode of transmission: The 2009 H1N1 virus is contagious and is spreading from human to human, like seasonal flu directly by cough, sneeze or talk. Or indirectly by touching infected surface or object and then touching there mouth or nose. 2009 H1N1 not spread by food (pork), assumed properly handled and cooked.

Prevention: Has three component: - Prevention in swine by vaccination and other facility management. - Prevention of pig to human transmission: mainly in farmers & veterinarians are encouraged to use face mask and gloves. - Prevention of human to human. Vaccination: single dose of swine flu vaccine are available for human. Chemoprophylaxis: oseltamivir, zanamivir.

Treatment : 1- Majority of people make a full recovery with out requiring medical attention or antiviral drugs. 2- Supportive care, relief pain, maintaining fluid balance and treatment of secondary infection. 3- Specific treatment: Oseltamivir cap. Or Zanamivir inhaled orally.

Avian influenza (bird flu)

Avian influenza in birds Avian influenza is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds.

Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence The “low pathogenic” and “highly pathogenic” forms.

Clinical picture: In birds : It ranges from mild infection with symptoms like ruffled feathers, drop in egg production or even no symptoms, to severe epidemic that kills up to 100% of infected birds within 48 hours.

Human infection with avian influenza viruses There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997.

Is it safe to eat poultry &poultry products? Does the virus spread easily from birds to humans? No Is it safe to eat poultry &poultry products? Yes, provided these items are properly cooked & properly handled during food preparation, H5N1 sensitive to heat (70 C˚ in all parts of the food, no pink parts, no runny yolks)

Antigenic shift: This mechanism produces a new subtype of influenza A v. through reassortment of the genetic material.

Despite the infection of tens of millions of poultry over large geographical areas for more than last 3-5 years, The total number of confirmed human cases of H5N1 reported till November 13, 2015 has reached 844 worldwide, 449 deaths (CFR = 59%). Most of them in Asia and the Middle East, and nearly all those who caught the virus were infected by handling or eating infected poultry.

Cumulative number of confirmed human cases of Avian Influenza A(H5N1): (2003 – 2015). Total Country   deaths cases 5 8 Azerbaijan 37 56 Cambodia 31 52 China 1 Djibouti 116 346 Egypt 167 199 Indonesia  2 3 Iraq (2006) Lao People's Democratic Republic Myanmar Nigeria Pakistan 17 25 Thailand 4 12 Turkey 64 127 Viet Nam 449 844 Source: WHO CFR = 59%

Warning signals of a pandemic Clusters of patients Closely related in time & place The detection of cases in health workers caring for H5N1 patients → Indicates human to human transmission Reservoir: Wild water fowl.

Treatment and vaccination for H5N1 virus in humans: The H5N1 virus is resistant to amantadine and rimantadine. Two other antiviral medications: Oseltamivir (commercially known as Tamiflu) and zanamivir (commercially know as Relenza).

C. Epidemic Measures The current way to prevent the disease in animal population during epidemics is to destroy infected animals. a. Health education to avoid contact with sick or dead birds. b. Avoid poultry farms and bird markets. c. Avoid contact with any surface or substance appear to be contaminated with poultry feces or secretions. d. Wash your hands frequently, if no water and soap, use alcohol based hand gels. e. Thorough cooking of all foods as poultry egg and meat. f. If you feel flu like symptoms, you should visit your doctor and stay away from contact with other people until prove that no H5N1 infection.