Avian Influenza (Bird Flu)
hsgm picture 5Avian Influenza (Bird Flu, Chicken Plague, Bird Flu) is a highly contagious disease caused by type A of influenza viruses observed as influenza viruses in humans, showing respiratory and digestive system symptoms in most of domestic and wild birds and mammals, resulting in death.
Influenza A viruses are classified according to hemagglutinin (H) and neurominidase (N) antigens. There are 15 subtypes of the influenza virus that causes disease in birds.
Avian influenza A virus, which infects poultry, is divided into two according to its ability to cause disease.
Those with high virulence lead to avian influenza with high pathogenicity, which can have a mortality rate of 100% in a flock. Birds can even die within the first day of symptoms.
Those with low virulence cause a much milder disease. Viruses responsible for both tables are currently H5, H7 and H9 subtypes.
How Is It Transmitted
Direct contact with the discharge of sick animals and especially feces; contact with food, water, supplies and clothing; Contact with water and seabirds that do not show clinical signs of disease may cause contamination. Especially dead or alive infected birds and people exposed to the waste of birds are transmitted through respiration and contact.
Avian influenza viruses generally do not infect humans directly and do not circulate between humans. There are very few natural infections in humans that have been reported to occur with avian influenza viruses. Cases in humans are thought to have developed as a result of contact with infected poultry or contaminated surfaces.
Although it is stated by the World Health Organization that there is no human-to-human transmission, suspicious transmission cases have been reported among healthcare workers, poultry workers and family members in the literature. It is understood that some strains of Avian Influenza A (H5N1, H7N7 and H9N2 etc.) can be transmitted from person to person, albeit in a very limited way, by healthcare workers, family members, poultry workers and those working in poultry disposal teams.
The disease can spread rapidly among farms within the country. They are transported from one place to another by infected vehicles, clothes and shoes.
The most important cause of epidemic is that wild migratory birds infect domestic birds directly or indirectly. Also, live bird markets are important in spreading the epidemic.
It can be transported from one country to another via international live poultry trade and migratory birds.
During the periods of infection, there is a risk of moving to settlements with vehicles and people entering and exiting wetlands. In risky periods, there is the possibility of the disease to be transported to settlements through hunting activities.
Another situation that creates a risk is the spread of the disease by uncontrolled vehicle and human movements from the settlements where the disease has occurred.
The disease has been reported to cause outbreaks in Asian countries, including the Republic of South Korea, Vietnam, Thailand, Cambodia, Indonesia, but the World Health Organization does not restrict travel to these countries.
What are the Symptoms
Cough with fever above 38 ° C
Shortness of breath,
One or more of diarrhea complaints can be seen together.
It is important to have a history of contact with poultry or a known or suspected avian influenza case in a country affected by H5N1 within 10 days prior to the onset of symptoms. Although the incubation period is 2-5 days on average, it has been reported that the disease develops after 17 days.
The course of the disease
The incubation period of avian influenza may be longer than the known human flu. In recent data, it is stated that the incubation period is two to five days, however this period may extend up to eight days. However, the upper limit has been reported as 17 days, possibly due to contact with unidentified infected animals or environmental sources.
The main clinical manifestations of avian influenza infection depend on the virus subtype causing the disease. Initial symptoms; Most patients have a high fever (typically higher than 38 ° C) and a flu-like illness with lower respiratory tract symptoms. Sore throat, cough and muscle pain can be seen. Upper respiratory symptoms are rarely present. Unlike infection with H7 or H9 viruses, conjunctivitis is rarely present in infection with avian influenza AH5N1. Diarrhea, vomiting, abdominal pain, pleuritic pain, nose and gum bleeding have been reported in some patients in the early period of the disease.
After the initial symptoms, lower respiratory tract symptoms usually develop and these findings are present at the patient's visit to the physician. Respiratory distress, tachypnea, and inspiratory rales are common. Sputum production varies and can be bloody at times. Almost all patients have pneumonia clinically. Radiological changes are in the form of diffuse, multifocal patch infiltrations, interstitial infiltrations and segmental or lobular consolidation with air bronchograms. Pleural effusion is uncommon. It is emphasized that radiological findings related to lung damage in surviving patients may continue for a few months after the disease. In severe cases, mechanical ventilator support may be required. Progression of respiratory failure is associated with diffuse bilateral ground glass infiltration and ARDS symptoms. Signs of renal failure, sometimes with cardiac dilatation and supraventricular tachyarrhythmias, are common.
Although children are more susceptible to avian influenza disease, children have been among the cases detected so far. In addition, avian influenza is more severe in children.
Complications such as pneumonia (viral or secondary bacterial), COPD exacerbation, myocarditis, myositis, pericarditis, renal failure, respiratory failure, ventilator-associated pneumonia, pulmonary haemorrhage, pneumothorax, pancytopenia, Reye's syndrome, and sepsis syndrome without documented bacteremia may develop. H5N1 has a more serious and lethal course compared to other avian influenza A strains.
How is it Diagnosed
The gold standard in laboratory diagnosis is virus isolation. Rapid laboratory verification of suspected human cases is usually performed by immunochromatographic or immunofluorescent detection of influenza virus antigens or by real-time-polymerase chain reaction (RT-PCR) of H5 specific RNA in respiratory samples. In addition, commercial ELISA kits are available that detect antibodies against viral antigens such as nucleoprotein.
Laboratory Criteria for Diagnosis At least one of the following must be positive.
a) Avian influenza A isolated from a clinical sample,
b) Detection of avian influenza A nucleic acid in a clinical sample,
c) Avian influenza A specific antibody response (four-fold or more increase or a single high titer).
Possible case Person meeting clinical and epidemiological criteria.
Strongly Probable case Person who tested positive for influenza AH5 or AH5N1 in a national reference laboratory not participating in the European Network Reference Laboratories for human influenza
Nationally confirmed case Influenza AH5 or AH5N1 test positive in a national reference laboratory with participation in the European Network Reference Laboratories for human influenza.
Person confirmed by a laboratory collaborating with WHO for case H5 confirmed by the World Health Organization
Who should sample be taken
With a history of contact with sick or dead poultry and with fever over 38 ° C
Shortness of breath
Appropriate samples will be taken from the nasopharyngeal swab or aspirate, nasal aspirate, BAL, tissue sample (biopsy) samples from patients with one or more of their complaints.
How is it treated?
Antivirals (Neuraminidase inhibitors oseltamivir and zanamivir) are used in the treatment of the disease. These medications should be started within the first 48 hours after symptoms start. Supportive care with oxygen and ventilator support forms the basis of treatment.
People with unprotected risky contact will receive prophylaxis. If there are unprotected contacts, prophylaxis is started in coordination with the infectious diseases specialist. Prophylaxis will be started by the Community Health Center where the contact is registered and will be followed up for 10 days.
Prophylaxis should be initiated as soon as possible, within the first 48 hours after initial contact with the confirmed or probable case. If this is not possible, prophylaxis can be started within 7 days after the last contact.
For chemoprophylaxis, oseltamivir should be given instead of standard influenza prophylaxis (1x75mg) at the therapeutic dose (2x75mg) for a short period of 5 days if the contact is not continuing, and for 10 days in intensive and continuous contacts.
Antivirals (Neuraminidase inhibitors oseltamivir and zanamivir) are used in the treatment of pediatric patients as well as adult patients. These medications should be started within the first 48 hours after symptoms start. Supportive care with oxygen and ventilator support forms the basis of treatment.
Oseltamivir dose in children is calculated as follows;
From 2 weeks to 1 year of age 6 mgkg a day in two doses,
1 year - 12 years old children (by kilogram)
2 x 30 mg for 15 kg and less,
2 x 45 mg between 15.1 - 23 kg,
2 x 60 mg between 23.1 - 40 kg,
40.1 kg and above 2 x 75 mg,
It is appropriate for the personnel involved in culling of birds with avian influenza to receive prophylaxis during culling and for 5 days after the last known contact, due to the intense exposure during culling.
What are the Ways of Protection?
If a person is definitively diagnosed or suspected of Avian influenza infection and does not require hospitalization;
Persons with risky contact for avian influenza infection should follow up for 10 days after their last contact for the presence of fever, cough, respiratory distress and other early symptoms such as headache, sore throat, nausea-vomiting and diarrhea.
Because of the risk of infecting other people in the home and in the community, they should live in a different room than other people in their home,
When coughing or sneezing, they should cover their mouth with a handkerchief (preferably with a tissue), used handkerchiefs should be placed in sealed and non-perforated nylon bags and thrown in a second nylon bag,
He should wash his hands frequently;
Wear a face mask when sharing the same environment with another person (house, street, public transportation vehicles, hospital, etc.),
Should not share personal belongings with others, and should not use household items such as cups, plates and towels; If he needs to use it, he should wash these items thoroughly with soap and water.
He should also monitor his symptoms and seek emergency medical help if his disease worsens.
Not to be sick
Necessary contact precautions (gloves and masks) should be taken before contacting with dead or live poultry with suspected disease.
When touching suspicious material with bare hands, hands must be washed with soap.
Inspected products should be consumed.
Poultry should be cooked well (60-70 degrees) under suitable conditions, and should not be consumed undercooked.
Those with suspected illness should immediately apply to health centers.
Family relatives and healthcare professionals who come into contact with people who are sick or suspected to be sick should wear protective masks and gowns.
The composition of the flu vaccine changes every year due to major or minor antigen changes in circulating viruses. Current flu vaccines are protective against human-specific influenza virus strains and do not protect against avian influenza virus. However, use of this vaccine is still recommended for people at high risk of contact in countries with a highly pathogenic avian flu epidemic among poultry. Thus, the possibility of any gene exchange during a co-infection with the human-specific influenza virus and the bird-specific influenza virus, and thus the emergence of a strain with pandemic potential, can be reduced.
Who is at Risk
People who come into direct contact with dead or alive sick animals or animal waste are at greatest risk. In addition, healthcare workers who come into contact with sick people are also at risk.
Pregnancy aggravates the course of avian influenza like other influenza types.
No special application is required for pregnant and breastfeeding people, and it is the same as the recommendations made for other patients. It is only recommended that the mother wear a face mask when approaching her baby.