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Outbreak of Avian Influenza (bird flu) in Human in

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Dr. Kanchan View Drop Down
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    Posted: December 07 2008 at 2:51am
Outbreak of Avian Influenza (bird flu) in Human in Bangladesh:
A Public Health Concern and What Should We Do Now?
A S M Alamgir, Ph.D.1; Kazi Mahboob Hassan, MPhil, MPH2; Mohammad Sabbir Haider, MSc, MPH1; M Mushtuq Husain, Ph.D.1
 
 
At last Bangladesh has been struck by Human Avian Influenza. Directorate General of Health Services (DGHS) in a press release on 22 May 2008 confirmed the existence of H5N1 Avian Influenza (Bird Flu) virus in a boy of 16 years in Dhaka. The boy was suffering from influenza in January this year. Sample was collected from this boy as a part of routine surveillance of influenza cases in human, conducted by Institute of Epidemiology, Disease Control & Research (IEDCR) and International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDRB).
 
“Bird Flu” vis-a-vis “Avian Influenza”?
 
“Bird Flu” is the colloquial term for Influenza of the birds. While the Avian (means related to birds) Influenza is the scientific term for the same disease of the bird. So they are synonymous.
 
Avian influenza viruses normally infect only birds and pigs. But Since 1959, viruses of the H5, H7, and H9 subtypes have crossed the species barrier to infect humans on 10 occasions. Most avian influenza viruses affecting humans have caused mild respiratory symptoms or conjunctivitis, with one important exception: the H5N1 strain.
 
Avian Influenza, H5N1 strain has first caused severe disease among human with high fatality in 1997. Studies comparing virus samples over time show that H5N1 has become progressively more pathogenic for mammals, and is now hardier than in the past, surviving several days longer in the environment. Evidence further suggests that H5N1 is also expanding its range of susceptible species.
 
The public health concerns
 
The outbreaks of Highly Pathogenic Avian Influenza (HPAI) in poultry that began in Asia in 2003 have, to date (December 07, 2008), been accompanied by 387 confirmed human cases, of which 245 have died. The majority of cases have occurred in previously healthy children and young adults. Most of these cases have been linked to close contact with infected poultry or their secretions. There is still no evidence of sustained human to human transmission.
 
But clearly H5N1 strain of Avian Influenza is of particular concern for several reasons: It can cause severe illness in human with a high fatality rate and H5N1 can mutate rapidly which leads to acquiring genes from human influenza viruses. Therefore if more humans become infected over time, the likelihood also increases for adaptation and obtaining sufficient genetic information to be easily transmitted from person to person. Such an event would mark the start of an influenza pandemic.
 
In the 20th century, the great influenza pandemic or the Spanish Flu pandemic (caused by H1N1 Strain of Influenza A virus of avian origin) of 1918–1919, caused an estimated 40 to 50 million deaths worldwide.  This pandemic was later followed by two milder pandemics in 1957–1958 (Asian Flu: 1-2 Million deaths worldwide) and 1968–1969 (Hong Kong Flu: About 700,000 death worldwide).
 
WHO and influenza experts worldwide agree that H5N1 has considerable pandemic potential. With the virus now endemic in large parts of Asia, the probability has increased. While it is impossible to accurately forecast the magnitude of the next pandemic, we do know that much of the world is unprepared for a pandemic of any size and for the widespread socioeconomic disruptions that would result from having large numbers of people quarantined, unwell or dying
 
Source of Infection and risk of transmission
 
Poultry
 
Till 21 May 2008, outbreak of Bird Flu has been confirmed in 287 commercial poultry farms and backyard farms across 47 districts in Bangladesh. The location of the farms include 128 upazillas and 14 metropolitan thanas. Culling have been conducted in 547 commercial poultry farms and backyard farms, number of culled chicken is 16,37,266.
 
The H5N1 Avian Influenza virus survives on contaminated raw poultry meat and can be spread through contaminated food products (e.g. frozen meat). In general, low temperatures increase the stability of the viruses. The virus can survive in faeces for at least 35 days at low temperatures (4°C);
In recent stability tests indicate that at 37°C H5N1 avian influenza viruses can be detected in faecal samples up to 6 days. The viruses can also survive on other surfaces such as the poultry house environment for several weeks.
 
Normal cooking (temperatures at or above 70°C) will inactivate the virus. To date there is no epidemiological evidence that people have been infected through consumption of properly cooked contaminated poultry meat. From these evidences, it can be concluded that well cooked poultry meat is safe but handling of frozen or thawed raw poultry meat before cooking can be hazardous if good hygienic practices are not observed.
 
In addition, in areas currently experiencing avian influenza outbreaks in poultry, the practice of marketing live birds with further extensive exposure to potentially contaminated parts of a chicken during home slaughtering, defeathering, eviscerating, etc. may pose a significant risk to persons involved in these activities. From the limited studies available, it appears that almost all parts of an infected bird are contaminated with the viruses. In poultry outbreak areas, contacts between humans and live poultry should be limited as much as possible by restricting movements of live birds and by using care in potentially hazardous activities such as raising free ranging poultry flocks in and around homes and home-slaughtering of poultry.
 
Eggs
 
The Avian Influenza virus can be found inside and on the surface of eggs. Although sick birds will normally stop laying eggs, eggs laid in the early phase of the disease could contain viruses in the albumen and yolk as well as on the surface.
 
The survival time of the viruses on surfaces such as eggs is sufficient to allow wide dissemination. Only proper cooking (no fluid portion remaining after frying or boiling) will be able to inactivate the virus present inside the eggs. However, there is no epidemiological evidence to suggest that people have been infected by consumption of eggs or egg products. 
 
Do pigeons  and crows carry and spread H5N1 viruses?
 
Studies conducted with the H5N1 avian influenza virus, which emerged in Asia in 2004, demonstrated an increased susceptibility of pigeons and crows to this virus compared to the 1997 Hong Kong virus. In Bangladesh, crows were found infected with H5N1, when examined during the mass death of crows in the cities of Dhaka and Chittagong in this year. It was suspected that these crows eaten the carcasses of H5N1 infected chicken, thrown away by people in the dustbin or open places. Thus, the general public should try to avoid unnecessary close contact with pigeons and crows, especially in places where pigeons and crows congregate in large numbers.
 
Is it safe to slaughter chicken and handle dead chicken in outbreak areas?
 
Wearing of protective gear, and practicing measures to prevent personal contamination, is essential. A large number of confirmed human cases are believed to have acquired their infection during the slaughtering or subsequent handling of diseased or dead birds prior to cooking. For this reason, such practices involving obviously diseased or dead birds must be stopped. In general, birds found in a diseased state or dead should never be used for human consumption.
 
In outbreak areas, some poultry species (such as domestic ducks) can be asymptomatic carriers of the virus. Vaccinated poultry can also carry the virus without showing symptoms. In these areas, it is important to effectively monitor the poultry population. In the absence of such monitoring systems, it is recommended that home-slaughtering be avoided. In non-outbreak areas, the likelihood of the virus being present in the poultry population is very low. Therefore, the likelihood of infected poultry being marketed and eventually handled by a consumer or a restaurant worker is considered to be very low. In this case, the public health risk related to avian influenza is negligible.
 
Hygiene in health-care settings
 
Presently, sound evidence on exact modes of human transmission of HPAI viruses is lacking. It is believed that multiple modes of transmission exist (large droplet, small particle aerosol, hand-contamination and self-inoculation, and possibly oral contamination), but their relative importance in sporadic HPAI infections is uncertain.
 
In hospital settings, it is important to protect both patients and health-care workers from the avian influenza infection. Strong hygiene practices are always a critical component of infection control. Of these practices, hand hygiene and surface cleaning are among the simplest and most cost-effective ways to prevent transmission of the highly pathogenic avian influenza virus.
 
Hygiene practices
 
Hand hygiene is a prerequisite to prevent the transmission of many infectious diseases. In environments where the HPAI virus may be present, hand hygiene, which includes hand washing and the use of alcohol-based hand rubs, is critical to prevent possible viral inoculation of the nose, mouth and conjunctivae by contaminated hands.
 
Hand hygiene is also necessary to prevent the transmission of nosocomial infections to other patients and healthcare workers. Pathogens are removed by the mechanical action of hand washing. Alcohol disinfects (kills the pathogens). If hands are visibly dirty, washing with soap and water is required prior to disinfection. Otherwise, alcohol-based preparations or washing are both appropriate. For soiled surfaces, cleaning MUST precede disinfection. Items and surfaces cannot be disinfected if they are not first cleaned of organic matter (patients’ excretions, secretions, dirt, soil, etc). Potent disinfectants are not required to kill influenza viruses; common soaps, dilute household bleach, even ashes are generally adequate. Use cleaning methods that do not produce aerosols (e.g. use wet dusting methods instead of feather dusting or dry sweeping) to mitigate any potential risk for virus transmission through direct inoculation (e.g. via inhalation or direct impact) into the respiratory (e.g. nose) or conjunctival mucosa. In healthcare settings, standard precautions are recommended for cleaning linen and laundry and managing clinical or nonclinical waste that may be contaminated with the highly pathogenic avian influenza virus.
 
Personal hygiene
 
There are basic good health habits that will help reduce the spread of influenza virus in the home or community settings. These include:
 • Cover your mouth and nose with a tissue when coughing or sneezing.
 • Wash your hands with soap often, especially: before, during, and after you prepare food; before you eat; after you use the toilet; after handling animals or animal waste; when your hands are dirty; and more frequently when someone in your home is sick.
• Avoid touching your eyes, nose or mouth. Infections are often spread when a person touches something that is contaminated with microorganisms and then touches his or her eyes, nose, or mouth.
-          Cleaning and disinfection of household surfaces likely to be contaminated by infectious secretions appears worthwhile.
-          However, presently, there is no evidence to support the efficacy of widespread disinfection of the environment or air.
-          As part of pandemic influenza planning, special attention should be given to teaching staff, children, and their parents on how to limit the spread of infection.
-          Programmes should already be teaching these things (e.g. use good hand washing; cover the mouth when coughing or sneezing; and clean toys frequently) to build habits that protect children from disease in general.
 
One of the best ways of preventing transmission of the H5N1 virus from animals to humans is through following these sensible hygiene practices - in food markets and in the home:
Ø        Don't prepare or eat either sick or dead animals - this is highly dangerous.
Ø        Avoid home slaughtering in outbreak areas.
Ø        Separate raw and cooked meat.
Ø        Ensure that food is cooked to the proper temperature, reaching 70°C in all parts of the food.
Ø        Clean and disinfect all work surfaces, equipment and utensils used for preparing poultry frequently.
Ø        Wash your hands regularly with soap and running water: before and after preparing food, before eating food, and after going to the toilet. If these practices are followed, both poultry and eggs are safe to eat.
The authors can be reached at: aalamgir@gmail.com
1Institute of Epidemiology, Disease Control and Research (IEDCR), Mohakhali, Dhaka 1212, Bangladesh.
2Infection Control and Infectious Diseases Research, Mount Sinai Hospital, Ontario, Canada.
Kanchan
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