The course of an influenza infection depends on factors relating to both the virus itself and the infected organism. The following factors influence the course of infection: physiological status of the patient in relation to age, nutritional status, history of the patient with respect to disease/health and related burden of chronic diseases, and level of […]
Influenza and the common cold are both respiratory illnesses but they are caused by different viruses. These two types of illnesses have similar flu-like symptoms, yet there are differences: Symptoms Cold Flu Fever Rare Usual; high (37.8°C to 38.9°C occasionally higher, especially in young children); lasts 3 to 4 days Headache Rare Common General Aches, […]
Clinical diagnosis The clinical symptoms of influenza are fairly characteristic, and during periods of epidemics enable a sufficiently reliable diagnosis to be made. For general practitioners, they form the basis for diagnosing influenza. During differential diagnosis, account must be taken of conditions such as: the common cold, infections caused by other types of viruses and […]
he course of influenza takes the form of a group of suddenly occurring symptoms such as: cough, fever above 38°C, muscular pain and/or headache. In the course of influenza infection, apart from the symptoms listed above, the following clinical symptoms often appear suddenly in the patient: generalized symptoms: shivering, general feeling of malaise, weakness, lack […]
The incubation period for influenza is one to four days. The period of infectivity depends on many factors, and has the following typical characteristics: in adults , it lasts six days – secretion of virus usually starts one day before the appearance of clinical symptoms and lasts approximately five days; in children, infectivity can last […]
Influenza A viruses continuously undergo antigenic evolution. Since the viral surface glycoprotein HA is the antigen against which virus-neutralizing antibodies are directed, it is primarily the antigenic variation of HA that is responsible for the immune escape of influenza viruses. Two distinct mechanisms of antigenic evolution can be identified: antigenic drift causes regular influenza epidemics, […]
The deadliness of an influenza virus mainly depends on its ability to efficiently suppress the innate immune system, thereby allowing high levels of virus replication. This is more likely to occur with pandemic influenza where the individual has not been exposed to the new virus subtype before and must rely on the innate immune response […]
When the influenza virus infects the cells of the respiratory tract, both innate and adaptive immune responses are stimulated. The innate immune response develops very quickly and controls virus replication during the early stages of infection. The cytokines produced during this early phase in turn facilitate the activation of antigen-specific adaptive immune mechanisms. Adaptive immune […]
How are influenza viruses transmited from human to human? Seasonal and pandemic influenza are highly contagious diseases and are spread primarily by coughing and sneezing. When they sneeze, people release tiny droplets of fluid into the air. Those tiny droplets can fly up to 1 metre and infect persons nearby by reaching susceptible cells of […]
In humans, the primary targets for influenza viruses are the epithelial cells in the airways and lungs. The viral HA binds to sialic acid residues on glycoproteins or glycolipids on the cell surface. The act of binding draws the virus into the cell membrane. The virus shell fuses with the cell membrane and moves through […]