influenza virus, symptoms, types, classification, prevention and medication

“Influenza (the flu) is a highly contagious respiratory illness caused by influenza virus.”

Influenza is highly infectious viral disease. It can cause mild to severe illness and at time can lead to death. It replicates in the endothelium of respiratory tract and causes cell destruction. This can be prevented by prevented by getting flu vaccination every year.

 CAUSES OF INFLUENZA:

Influenza commonly called flu is an illness caused by RNA virus of family ORTHOMYXOVIRIDAE the influenza virus that infect respiratory tract of many animals, birds and humans.

 SYMPTOMS OF INFLUENZA VIRUS:

• Fever
• Cough
• Sore throat
• Headache
• Gastric vomiting
• Intestinal diarrhea
• Runny or stuffy nose
• Muscle or body aches
• 
  COMPLICATIONS:

 The complications of influenza virus are as follows:

• Pneumonia
• Dehydration
• Asthma
• Diabetes

EFFECTS OF VIRUS:

The flu effects throat, nose, lungs and other parts of body. Unlike, common cold, flu comes on suddenly can make people very sick for a week or longer or can send them to hospital.

 SPREADING   OF INFLUENZA VIRUS:

v  Influenza virus easily spreads from person to person via respiratory droplets when an infected person coughs and sneezes.

• v  It also spreads when someone touches a surface contaminated with virus.
• v  Airborne transmission of virus is possible, when an infected person is talking.
• v  Adults shed infectious influenza virus 1-2 days before any symptom appears.
• AVERAGE OF INFLUENZA IN US:

Every year in US:

• v  5% to 20% of population gets flu.
• v   More than 200,000 people are hospitalized from flu complications.

 DEATH RATE IN US:

In the past 30 years 3,000 to 49,000 people die from flu every year.

 STRUCTURE:

The structure of influenza virus is as follows:

 SHAPE AND SIZE:

  Influenza virus is roughly spherical ranging from 80-120 nm in diameter.

 OUTER MEMBRANE:

Outer membrane is a lipid membrane which is taken from host cell in which virus                                                    multiplies. Inserted into lipid membrane are approximately 500 spikes like projections which are proteins. These proteins are actually glycoprotein because they consist of protein linked to sugar known as HA (haemagglutinin) and NA (neuraminidase).

 MATRIX  PROTEIN:

Beneath lipid membrane is a viral protein called M1 or matrix protein. This protein forms   a shell and gives rigidity and strength to lipid envelop.

 

 

CENTRAL CORE:

 The central core contains viral RNA genome and other viral proteins that package and         protect this RNA. RNA tends to be single stranded but in some cases it is doubled.

 LIFE CYCLE:

The life cycle of influenza virus is as follows:

 VIRAL ENTERY:

For virus to reproduce and thereby establish infection, it must enter cells of host organism and use those cell materials. To enter the cell, proteins on the surface of the virus interact with proteins of cell. Attachment or adsorption occurs between viral particle and host cell membrane. A hole forms in the cell membrane, then virus particle or its genetic contents are released into the host cell, where replication of viral genome may commence.

 VIRAL REPLICATION:

Next, a virus must take control of host cell replication mechanism. At this stage, distinction occurs between susceptibility and permissibility of host cell is made. After control is established and environment is set for viruses to making copies of itself, replication occur quickly by million.

 VIRAL SHEDDING:

After virus has made copies of itself, it has usually exhausted the cell of its resources. The host cell is no longer useful to virus, therefore cell often dies and newly produced viruses must find a new host. The process by which virus progeny is released to find new host is called shedding. It is last stage in viral life cycle.

 VIRAL LATENCY:

Some virus can hide within a cell, either to evade host cell defense or immune system or simply because it is not in the best interact of virus to continually replicate. This hiding is deemed latency. During this time, virus does not produce any progeny, it remains inactive until external stimuli- such as light or stress- prompts it to activate.

CLASSIFICATION:

Influenza virus is classified into three types which are as follows:

• v Influenza A
• v Influenza B
• v Influenza C

 

INFLUENZA A:

Influenza virus is divided into subtypes on their basis of two surface antigens (foreign protein) - haemagglutinin (H) and neuraminidase (N). There are 16 different HA and 9 NA. All viruses a subtype circulates in aquatic birds. Only some of these subtypes have been identified in humans. Influenza A virus infects a variety of other mammals including non- human primates, pigs, horses, whales and mink etc.

 INFLUENZA B:

Influenza B does not have any subtype. It exclusively infects humans and is less common than influenza A. This type of influenza mutates at a rate 2-3 times lower than influenza A. This reduced rate of antigenic change, combined with its limited host range ensures than pandemics of influenza B does not occur.

 INFLUENZA C:

Influenza C is less common than other types. It infects humans, dogs and pigs sometimes causing both severe illness and local epidemics. It usually causes mild disease in children.

 PREVENTION:

Influenza virus can be prevented by following ways:

v  Avoid close contact with sick people.

v  Cover your mouth and nose.

v  Clean your hands.

v  Avoid touching your eyes and nose.

v  Practice other good health habits such as:

v  Plenty of sleep.

v  Manage your stress.

v  Drink plenty of fluids.

v  Eat nutritional food.

v  Yearly vaccination.

 MEDICATION:

Medicines which inhibits influenza virus are as follows:

• v Amantadine and Rimantadine is used in the prevention and treatment of influenza A.
• v  Oseltamivir and Zanamavir inhibit neuraminidase which release new virions.