Airborne transmission influenza

Fast Shingles Cure

Fast Shingles Cure by Bob Carlton

Get Instant Access

Influenza is a disease of the respiratory tract caused by members of the Orthomyx-oviridae. Transmission occurs as a result of inhaling airborne respiratory droplets from an infected individual. Infection by the influenza virus results in the destruction of epithelial cells of the respiratory tract, leaving the host open to secondary infections from bacteria such as Haemophilus influenzae and Staphylococcus aureus. It is these secondary infections that are responsible for the great majority of fatalities caused by influenza. Generally, sufferers from influenza recover completely within 10-14 days, but some people, notably the elderly and those with chronic health problems, may develop complications such as pneumonia.

The influenza virus has an envelope, and a segmented ( —) sense ssRNA genome (Figure 10.19). The envelope contains two types of protein spike, each of which plays a crucial role in the virus's infectivity:

• Neuraminidase is an enzyme which hydrolyses sialic acid, thereby assisting in the release of viral particles.

• Haemagglutinin enables the virus to attach to host cells by binding to epithelial sialic acid residues. It also helps in the fusion of the viral envelope with the cell membrane.

Both types of spike act as antigens, proteins that stimulate the production of antibodies in a host. One of the reasons that influenza is such a successful virus is that the 'N' and 'H' antigens are prone to undergoing changes (antigenic shift) so that the antigenic 'signature' of the virus becomes altered, and host immunity is evaded. Different strains of the influenza virus are given a code denoting which variants of the antigens they carry; the strain that caused the 1918 pandemic, for example, was N1H1, while the one responsible for the outbreak of 'bird flu' in SE Asia in 2003/4 was H5N1.

Table 10.3 Some important viruses of humans

Virus

Family

Disease

Genome type

Adenovirus

Adenoviridae

Respiratory infections

dsDNA

Ebola virus

Filoviridae

Haemorrhagic fever

( — ) ssRNA

Epstein-Barr virus

Herpesviridae

Infectious

dsDNA

mononucleosis

Hepatovirus A

Picornaviridae

Hepatitis A

(+) ssRNA

Herpes simplex Type I

Herpesviridae

Cold sores

dsDNA

Herpes simplex Type II

Herpesviridae

Genital warts

dsDNA

Human immunodeficiency

Retrovir idae

Acquired immune deficiency

(+)ssRNA*

virus (HIV)

syndrome (AIDS)

Human papillomavirus

Papovaviridae

Warts

dsDNA

Influenza virus

Orthomyxoviridae

Influenza

( — ) ssRNA

Lassa virus

Areiiaviridae

Lassa fever

( — ) ssRNA

Morbillivirus

Par amy xovir idae

Measles

( — ) ssRNA

Norwalk virus

Calciviridae

Enteritis

(+) ssRNA

Paramyxovirus

Par amy xovir idae

Mumps

( — ) ssRNA

Polio virus

Picornaviridae

Poliomyelitis

(+) ssRNA

Rabies virus

Rhabdoviridae

Rabies

( — ) ssRNA

Rhinovirus

Picornaviridae

Common cold

(+) ssRNA

Rotavirus

Reoviridae

Enteritis

dsRNA

Rubella virus

Togaviridae

German measles

(+) ssRNA

Smallpox virus

Poxviridae

Smallpox

dsDNA

Varicella-Zoster

Herpesviridae

Chicken pox, shingles

dsDNA

Yellow fever virus

Flaviviridae

Yellow fever

(+) ssRNA

1 The genome of HIV, like that of other retroviruses also has a DNA phase. See the text.

1 The genome of HIV, like that of other retroviruses also has a DNA phase. See the text.

Tied And Penetrated
Figure 10.19 The influenza virus. The RNA segments are bound to protein, forming a nucleocapsid, and are surrounded by further protein. The two types of spike assist in the attachment and penetration of the virus into its host

Was this article helpful?

0 0
Swine Influenza

Swine Influenza

SWINE INFLUENZA frightening you? CONCERNED about the health implications? Coughs and Sneezes Spread Diseases! Stop The Swine Flu from Spreading. Follow the advice to keep your family and friends safe from this virus and not become another victim. These simple cost free guidelines will help you to protect yourself from the swine flu.

Get My Free Ebook


Post a comment