المرحلة الرابعة طب مجتمع د.مؤيد العدد14 5\12\2017 326 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. The excess mortality varies and depends on the prevalent virus type.

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, haemoglobinopathies, 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. Its effective chemoprophylaxis of influenza A but not B (about 70-100 %). Same indications as vaccine. The amantadine side effect on CNS is 5-10% and increased in elderly and those with impaired renal functions. Rimantadine cause fewer CNS side effects. 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. Concurrent disinfection: Not Applicable. Quarantine: Not Applicable. Protection of contacts: by chemoprophylaxis. Investigation of contacts and source of infection: none 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.

History : Swine influenza was first proposed to be a disease related to human influenza during 1918. The first identification of an influenza virus as a cause of disease in pigs occurs in 1930. 1976 U.S. out break in Fort Dix, 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), 2007 Philippine out break in swine.

2009 out break in Human : - On March 17, 2009 the earliest cases occurred in Mexico. - After few days around 2000 cases in Mexico. April 26, 2009 the U.S. declared a national public health emergency involving H1N1. May 5, 2009 > 400 cases of H1N1 confirmed in nearly all states with in the U.S. , and > 1000 cases in 21 countries world wide. Human cases H1N1 have been reported world wide. Jun 11, 2009 WHO declared onset of influenza pandemic.

Up to march, 2010 world wide > 213 countries reported lab Up to march, 2010 world wide > 213 countries reported lab. confirmed cases. In Iraq total number of cases 85, deaths 5 till end February 2011. Globally: CRF 0 .02 %. The most common cause of death is respiratory failure. - August, 10, 2010 WHO declared post pandemic period

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), eating properly handled and cooked pork product is safe.

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. 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.

However, in January 2015 it was found in a wild duck in the United States (U.S.), and it has also been isolated in pigs, cats, dogs, stone martens, and lions and tigers in captivity.

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.

Human infection with avian influenza viruses Most cases of avian influenza infection in humans have resulted from contact with infected poultry or surfaces contaminated with secretion/excretions from infected birds.

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)

Signs and symptoms A person with H5N1 will develop serious symptoms Signs and symptoms A person with H5N1 will develop serious symptoms. Initial symptoms include a high fever, over 38 degrees centigrade, lower respiratory tract symptoms, and, less commonly, upper respiratory tract symptoms. headache, and an upset stomach. Deterioration can be rapid. It can be fatal in 60 percent of cases.

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 August 10, 2012 has reached 608 worldwide, 359 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): 10 August 2012 . Total Country   deaths cases 5 8 Azerbaijan 19 21 Cambodia 28 43 China 1 Djibouti 60 168 Egypt 159 191 Indonesia  2 3 Iraq Lao People's Democratic Republic Myanmar Nigeria Pakistan 17 25 Thailand 4 12 Turkey 61 123 Viet Nam 359 608 Source: WHO CFR = 59%

The first outbreak of H5N1 bird flu was in December 2003 The first outbreak of H5N1 bird flu was in December 2003. Since then, over 700 cases have been reported, in Africa, Asia, and Europe. The highest numbers have been in Indonesia, Vietnam, and Egypt. The most recent case of H5N1 was reported in Malaysia in March 2017. It killed a number of chickens, but no human cases were reported. It is not easy for humans to catch it, but it is fatal in 60 percent of cases

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 I.P: for H5N1 avian influenza : 2 – 8 days and possibly as long as 17 days.

In 2009, the FDA approved the AVantage A/H5N1 Flu Test, which detects influenza A/H5N1, or bird flu, from nose or throat swabs collected from patients with flu-like symptoms. In less than 40 minutes, the test can identify a specific protein (NS1) that indicates the presence of A/H5N1 virus subtype. 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)

Draw backs of the vaccine There is no commercially available vaccine to protect humans against H5N1 virus that is being seen in Asia and Europe. However, vaccine development efforts are taking place. According to the World Health Organization (WHO), a vaccine for H5N1 exists, but it is not yet ready for widespread use

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.