Influenza and Other Acute Respiratory Diseases (ARDs) AssayNotes

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1. Influenza A and B

Influenza viruses are unique in their ability to cause sudden, pervasive illnesses in all age groups of human population on a global scale. Three “pandemics” associated with “shift” of surface viral glycoproteins (HA, NA) have occurred in the past century. One of them, “Spanish flu”, in 1918 was responsible for more than 20 million deaths worldwide, primarily in young adults. Annual influenza epidemics associated with different virus types or subtypes caused excess morbidity and mortality especially in groups of high risk. In spite of special clinical signs of influenza (such as sudden fever (>38 °C), pronounced intoxication (headache, myalgias), dry cough, shortness of breath and sternal pain) common clinical picture varied in dependence of age, individual immunity condition, accompanied person pathology and pathogenicity of virus strain. Diagnosis during pre- and inter-epidemic periods became available as a result of laboratory test applications. Laboratory diagnosis for influenza is based on direct examination and paired serum specimens serological assay. Immunofluorescence (IF) testing performed directly on nasopharyngeal secretions. EIA tests are often more objective and more sensitive than IF for direct detection. These diagnoses are necessary for etiotropic chemotherapy prescription.

2. Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus is one of the most important respiratory pathogens in infants and children provoking considerable morbidity, which often requires bed care. Severe diseases caused by Respiratory Syncytial virus are most common among infants during the first six months of life and patients with immunodeficiency. Serious lesions of the lower respiratory tract induced by Respiratory Syncytial virus (bronchitis, bronchiolitis, pneumonia) are one of the important causes of mortality in infants. 60-70 % of infants less than six months of age fail to induce detectable antibody response to natural infection. Repeated infections with Respiratory Syncytial virus are common and result in neutralizing antibody formation.

3. Adenovirus

Adenoviruses are a large group (more than 80 types) of agents, which induce respiratory infections among human beings, animals and birds. Clinical pattern of adenoviral infection is characterized by pronounced pharyngitis, conjunctivitis, general intoxication and pulmonary lesions with high fever in children. Adenovirus types 3, 4, 7, 14 and 21 often spread in military units and account for 72 % of ARDs among recruits. A considerable part of these diseases results in hospitalization. Adenovirus types 3, 4, 7, 8 and 19 are known as causative agents of epidemic keratoconjunctivitis. Some types of adenoviruses provoke outbreaks of gastroenteritis with long (more than 2 months) carriage of viruses.

4. Parainfluenza

Parainfluenza virus types 1-3 are common agents of acute respiratory infections predominating among children less than 5 years old. They induce about 15 % of acute respiratory infections. They are mostly causative agents of severe croup, bronchitis, bronchiolitis and pneumonia (Parainfluenza virus type 3) in infants. Children can be infected with Parainfluenza virus several times during one year.

5. Avian influenza

Avian influenza viruses occurring naturally among birds cause avian influenza infection. Usually “avian influenza virus” refers to influenza A viruses found mainly in birds, but infections with these viruses can occur also in humans. Avian influenza was first identified over 100 years ago during an outbreak in Italy. Since then, the disease has cropped up at irregular intervals in all world regions.
There are many different subtypes of type A influenza viruses and they differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). Many different combinations of HA and NA proteins are possible and each combination represents a different subtype. Of the 16 different hemagglutinin types only strains within the H5 and H7 subtypes cause highly pathogenic avian influenza, which is highly contagious and rapidly fatal in susceptible avian species. When highly pathogenic influenza H5 viruses cause outbreaks, the mortality rate among poultry is usually between 90 %- 100 %.

6. Newcastle disease virus (NDV)

Newcastle disease (ND) is a highly contagious and sometimes fatal illness affecting many domestic and wild bird species. The causal agent, Newcastle disease virus (NDV), is a negative-sense single-stranded RNA virus. NDV affects the respiratory, nervous, and digestive systems. Clinical signs are extremely variable depending on the strain of virus, species and age of bird, concurrent disease, and pre-existing immunity. NDV is so virulent that many birds die without showing any clinical signs.
Transmission occurs by exposure to foecal and other excretions from infected birds, and through contact with contaminated food, water, equipment and clothing. Virus-bearing material can be picked up on shoes and clothing and carried from an infected flock to a healthy one. Exposure of humans to infected birds (for example in poultry processing plants) can cause mild conjunctivitis and influenza-like symptoms, but NDV otherwise poses no hazard to human health. MAbs are negative with parainfluenza type 3 and avian influenza hemagglutinins.


Search Influenza references from PubMed.

Research Courtesy of HyTest

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