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28 Cards in this Set

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What are Orthomyxoviridae?
They are spherical virions. At the virion center lie 8 segments of negative stranded RNA with a nucleocapsid protein. The outer membrane is studded with long glycoprotein spikes.
What are the 2 types of glycoprotein spikes found?
1. Hemoagglutinin activity(HA).
2. Neuroaminodase activity(NA).
Anchoring the bases of each of these spikes on the inside of the viral lipid bilayer are membrane proteins(M proteins).
What is Hemagglutinin?
It can attach to host sialic acid receptors. These receptors are present on the surface of erythrocytes, so viruses with HA glycoproteins cause hemagglutination when mixed with red blood cells.
These receptors also exist on respiratory tract cell membranes. HA is needed for adsorption.
What is neuroaminodase?
Neuraminic acid is an important component of mucin, the substance covering mucosal epithelial cells and forming an integral part of the hosts upper respiratory defense barrier.
What does neuraminadase do?
NA cleaves neuraminic acid and disrupts the mucin barrier, exposing the sialic acid binding sites beneath.
What are the three types of influenza?
A,B, and C. These types have many strains separated by antigenic differences in HA and NA.
Type A infects humans, other mammels(swine, etc) and birds. TYpe B and C have only been isolated from humans.
What is antigenic drift?
During viral replication, mutations can occur in the HA or NA, leading to changes in the antigenic nature of these glycoproteins. The changes are small.
What is antigenic shift?
With this, there is a complete change of the HA, NA or both. This only occurs with influenza type A because the mechanism involves the trading og RNA segments between animal and human strains. As a result, RNA segments may be mispackaged into another virus.
The new HA and NA antigens are given number subscripts to differentiate them. What does this mean?
The pandemic of 1889 was caused by a virus with an H2 hemagglutinin, the pandemic of 1900 was caused by a new virus with H3 hemagglutinin.
In 1918 a swine flu virus transferred its HA to a human virus and so was called "Hswine hemagglutinin(HSW).
Regarding global pandemics, what what are the HA/NA descriptions of some of the flu viruses?
1918-H1N1; Spanish flu
1947-H1N1
1957-H2N2; Asian flu(low mortality)
1968-H3N2; Hong Kong flu
2005-H5N1; Avian flu(pandemic potential).
What is the Avian flu?
In 1997 a new starin of avian influenza(type A, H5N1), was transmitted from infected poultry to humans in Hong Kong. It had supercharged HA similar to the 1918 pandemic. Fortunately, the virus was poorly transmissible to humans and was controlled by destroying the poultry in Hong Kong.
What are some of the complications of Influenza?
It can lower the host defenses against many bacteria. secondary bacterial pneumonias by Staph. aureus and Strep. pneumoniae and others are common.
What is Reye's syndrome?
Children given aspirin when they have influenza or varicella(chicken pox) can develop a severe liver and brain disease called Reye's syndrome. Acetaminophen is preferred to aspirin.
Influenza viruses are grown in mass quantities in chick embryos, which are then inactivated, purified and used as vaccines. TRUE/FALSE
TRUE. Scientists choose 3 strains that are circulating in the population or expected to cause an outbreak in the next season.
Is there a viable treatment for the flu?
Amantadine and Rimantidine prevent the uncoating of influenza A.
Sanamivir(inhaled) and Oseltamivir(oral) are NA inhibitors, which can shorten the course of influenza A and B.
What are Paramyxoviridae?
They are similar to that of the Ortho species. However,, the negative stranded RNA is in a single strand, not segmented. Ha and NA are part of the same glycoprotein spike, not 2 different spikes.
They also possess a fusion(F) protein, that causes the infected host cells to fuse together into multinucleated giant cells(syncytial).
Name 4 paramyxoviridae that cause human disease?
1. Parainfluenza virus
2. Respiratory syncytial virus
3. Mumps virus
4. Measles virus.
What is Parainfluenza virus?
It causes upper respiratory infection in adults ranging from cold symptoms to bronchitis and flu-like illness.
Croup is a parainfluenza infection of the larynx.
What is Respiratory Syncytial Virus(RSV)?
It causes respiratory infections and contains an F protein that causes formation of multinucleated giant cells. It lacks the HA and NA glycoproteins.
It can be prevented in a high percentage of cases with "palivizumab", which is a monoclonal antibody against RSV.
RSV immune globulin is also available.
What is the Mumps virus?
It replicates in the upper respiratory tract and in regional lymphnodes and spreads via the blood. The parotid gland is often involved.
About 3 weeks after initial exposure to mumps virus, the parotid gland swells and becomes painful. TRUE/FALSE
TRUE. The testes are also frequently involved. About 25% of infected males will develop orchitis.
There is only one antigenic type, and a live attenuated viral vaccine is a part of the trivalent measles mumps rubella(MMR) vaccine. TRUE/FALSE
TRUE.
What is the Measles virus?
There are still 2 million deaths annually worldwide due to this virus, despite vaccine protocols. There are only about 2,900 cases in the U.S. It is also called Rubeola.
Is measles contagious?
It is highly contagious and spreads through nasopharyngeal secretions. The virus multiplies in the resp tract and conjunctival membranes.
What is meant by measles prodrome?
Prior to the rash, the patient suffers from prodromal illness with conjunctivitis, eyelid swelling, photophobia, high fevers, cough, rhinitis and malaise.
What are Koplik's spots?
A day or two, before the rash, the patient develops small red based lesions with blue white centers in the mouth.
Can the measles virus disseminate?
It can to many organ systems and cause damage, causing pneumonia, eye damage, myocarditis and occasionally encephalitis. About 10% who develop this may die.
It has associated with spontaneous abortion.
What is Subacute sclerosing panencephalitis(SSPE)?
This is caused by the measles virus. many years after a measles infection the child or adolescent may have slowly progressing CNS disease and incoordination.
The MMR vaccine which is a live attenuated virus is preventative.