ARD or ARVI. What is the difference?
O. Timokhina, Nesvizh
Acute respiratory viral infections (ARVI) or ARD (acute respiratory diseases) are airborne illnesses caused by various activators: viruses, bacteria, chlamydia and mycoplasma. In addition, associations of causative activators are possible: viral-bacterial, viral-mycoplasmal and viral-viral ARD (mixed infections).
The ARD group comprises causative agents various in forms but similar in their clinical display; they differ in severity of development and localisation within the respiratory tract, with respiratory infections being most common, accounting for about 75 percent of all infections.
ARVI (acute respiratory viral infections) are the most widespread of human illnesses, accounting for up to 90 percent of all cases of infectious disease. Viruses causing ARVI affect the epithelial cells (those from nose and throat to lungs). Flu is the best known of these viruses but others, no less significant, include parainfluenza, adenovirus, rhinovirus, rotavirus and reovirus. Each has variants (four for parainfluenza but several dozen for flu) which makes them difficult for the body to fight off.
Viruses die quite quickly in an external environment, but are transmitted from one person to another very easily, being airborne. It can take just a few hours for symptoms to become apparent after initial infection, but this incubation period may also take up to four days. Those who are sick transfer the virus through coughs and sneezes; anyone within a distance of one metre is at risk — with the virus entering through eyes, nose or mouth. Contact with infected surfaces is also dangerous, since we tend to touch our faces repeatedly through the day. Of course, frequent hand-washing can help deter spreading viruses in this way.
Once infected, symptoms include high temperature, sneezing, cough, rhinitis, fever, and muscle pain, with particular viruses affecting particular sections of the respiratory system. Rhinovirus affects the nose mucous membrane, while parainfluenza is felt in the throat and trachea, and flu makes the trachea and bronchial tubes sore.
Individual symptoms of ARVI depend, primarily, on which part of the respiratory tract is most inflammed. Rhinitis involves the mucous membrane of the nose, while pharyngitis affects that of the throat, and rhinopharyngitis involves the nose and throat simultaneously. Tonsillitis inflames the palatal tonsills, laryngitis is centred in the throat and tracheitis inflames the trachea. Bronchitis involves the bronchial tubes, while bronchiolitis affects the smallest bronchial tubes: the bronchioles.
Various serotypes of viruses differ in antigenic structure, but thrive in situations of overcrowding, spreading most easily. Resistance is lowered when the body is cold, under stress or suffering from nutritional deficiency. Unsurprisingly, sickness rates rise during the autumn-winter period.
The severity of ARD development is defined by the extent of catarrhal-respiratory symptoms. Intoxication is the basic clinical sign of acute flu, distinguishing it from other ARD. Infection generalisation (involvement of other systems within the body) can be the result of bacterial ARD: meningococcal rhinopharyngitis can turn into meningitis; pneumococcal bronchitis can develop into pneumonia; and staphylococcus is capable of causing rhinosinusitis or otitis.
Hospitalisation may be necessary for those with ARD if complication arise or other disease is evident. Those living in crowded communities, or located remotely from medical facilities may be good candidates for admission to hospital, as may be those advanced in years, or who have restricted mobility.
By Tatiana Zhukova, doctor of higher category, D.M. Ph.D.