Welcome to the Virology Land.

Sunday, January 25, 2009

Today we will be discussing about Flaviviridae.

History of Flaiviviridae:

~Arbovirus (arthropod-borne viruses)
-Alphaviruses: Togaviridae
-Flaviviruses: Flaviviridae

~Flaviviridae
-Flavivirus

~Pestivirus : Yellow Fever, Dengue, West Nile
-Hepacivirus : Hepatitis C

Lets talk abt Pestivirus

Natural host(reservoir):Allows amplification of the virus and maintain viremia to allow acquisition by the arthropod.
Host: allows infection, but not necessarily maintain viremia.
Dead-end Host: An host from which infectious agent is not transmitted on.

Properties:

-Spherical enveloped virion, 40-50 nm
-Inner core protein C
-Membrane / matrix protein M
-Envelope with glycoprotein peplomers (E)
-Single linear 11 kb positive sense ssRNA :Infectious mRNA
-3’ polyadenylated tail and 5’ cap
-Cytoplasmic replication (perinuclear)
-Polyprotein from genomic RNA cleaved
-3 structural proteins
-Several non-structural proteins

Now we will talk abt the diseases that are caused by Flaviviridae that is currently troubling the nation now...

Dengue

1. Properties
-Most important arbovirus presently
-Southeast Asia to Americas to Pacific to Africa
-Non-fatal dengue fever (DF)
-Usually fatal dengue haemorrhagic fever (DHF) / dengue shock syndrome (DSS)
-4 distinct serotypes based on neutralisation test.
-DEN-1, DEN-2, DEN-3 and DEN-4
-DEN-2 shows greatest antigenic and genotypic distance from the others
-Protective immunity after infection homotypic

News Update
2007, 1500 cases were reported in the first 19 weeks of 2007.
50% higher than 2006.
Mainly due to Dengue 2, the strain causing 60% of these case.

2.Dengue Infection Cycle

3.Dengue Fever

-Many infections asymptomatic
-Acute infection resulting in fever, severe headache (frontal), retro-orbital pain, nausea and vomiting
-Severe muscle and bone pain
-Severe arthralgia (joint swelling -mainly back) break bone fever
-Maculopapular rash just before recovery

B.Dengue Haemorrhagic Fever/ Dengue Shock Syndrome

-Prior infection and age key factors in DHF and DSS
-Seldom occurs in individuals above 15 years
-Similar to yellow fever in biphasic nature:
~Initial symptoms similar to DF followed by remission
~Sudden deterioration of patent condition
-Severe prostration, hypotension, circulatory collapse, bleeding and shock
-Bleeding
~Petechiae in skin, mucous membranes (mouth)
~Injection and punction sites
~Gastrointestinal bleeding
~Haemorrhagic pneumonia
-WHO grading:
~Grade I : Fever with non-specific, constitutional symptoms and the only haemorrhagic manifestations being a positive tourniquet test
~Grade II : As for grade I, but with specific haemorrhagic manifestations
~Grade III : Signs of circulatory failure or hypotension
~Grade IV : Profound shock with pulse and blood pressure undetectable
-Pathogenesis
~Not well understood despite intensive study –2 theories
~Virulent strain theory
~Some strains more virulent than others
~Molecular studies show variations in sequences amongst different strains within serotypes
~Early evidence pointed to DEN-2
~Antibody enhancement
~Main theory for DHF / DSS
~Main cell target of DEN: monocytes / macrophages
~Most cases of DHF/DSS had prior infection or infants below 1 year had maternal Ab
~Monkey experiments showed similar enhancement
-Possible cause

~Immune system overreacting
~Sever Acute Respiratory Syndrome

-Transmission - Aedes Mosquito (Female)

-Control:
1.Use of Insecticides
2. Use of Mosquito Screen
3. Removal of Stagnant water

Yellow Fever

1.Properties
-Type species of genus flavivirus
-"flavi" –"yellow" in Latin
-Tropical disease in Latin America and Africa
2.History
-Incubation period: 3-6 days
-Viraemia, infectious, headache, malaise, nausea, lassitude, muscle ache (3 days)
-Flushing of head & neck, conjunctival injection, strawberry tongue

3.Severe Yellow Fever
-Remission after acute yellow fever
-Haemorrhagic, hepatic and renal disease
-Fever, vomiting, abdominal pain, dehydration, prostration
-Haemorrhagic / coffee-ground diathesis (black vomit)
-Bleeding from puncture sites of injections and drip needles
-Jaundice

-Massive haematemesis / haemoptysis / intra-abdominal bleeding
-Renal failure, hypotension, shock
-Virus absent from blood, but antibody titre high –implying autoimmunity may play major role
-Mortality 20-50%
-Survivors suffered extended chronic jaundice before full recovery; hepatic and renal failure may persist
4.Transmission:

5.Control:
- Attenuated Vaccine

West Nile Fever

1.History
-Originated in Uganda
-Discovered in 1937
-Common in Africa, West Asia, Europe, Middle East
-Spread in US (New York) began in 1999
-Epidemic in US in 2002
2.West Nile Fever
-Mainly mild to no symptoms
-Fever
-Headache, body aches
-Skin rash
-Swollen lymph glands
-Severe symptoms
~Crossing blood-brain barrier
~Encephalitis
~Meningitis
-Mainly in persons above 50 years
3.Transmission:

CONTROL FOR ALL THE DISEASES:

1.Use of Insecticides
2. Use of Mosquito Screen
3. Removal of Stagnant water

The purpose of going through Flavivirdae is because we want to help our peers in their revision and also at the same educate the public on the diseases thats troubling us rite now..

5:31 AM

Friday, January 2, 2009

As you all know, we touched on rhino virus yesterday. However, it seems that people misunderstood cold for flu sometimes. Like when they are sneezing and you ask whats wrong and they will reply oh I think I have flu. Well, that is a common understanding that we have!

Well cold and flu are two different viruses! So today we will discuss about flu.
Flu or more commonly known as Influenza virus is a genera from the virus family called Orthomyxoviridae and it is divided into types Influenza virus A and Influenza virus B. There is a flu vaccine is available but it is very expensive.

The morphology is that it is typically spherical, enveloped, pleomorphic, there are spikes on the envelope, groups of HA or NA in ratio of 5:1. The genome contains single stranded (-) RNA in 8 segments, 3 polymerase polypeptides with each segment and 5’ and 3’ end of all segments are highly conserved.

The Pathogenesis is the respiratory tract in human, affinity of the HA for receptors in the epithelium of the tract, innate resistance, mucus cilia, immunocompromised elderly and premmies and there are also existing antibodies like anti-HA Ab and IgA,IgG. There are also macrophages, NK cells and cytokines.

The symptoms are high fever, prominent headache, usual aches and pains, common fatigue and common cough.

The lab diagnosis is throat swab/gargle/nasal wash, virus culture (MDCK cell line or chick embryo), direct EIA (HA) and PCR.

The epidemiology is that it is present all throughout the year where incubation (1-4 days) will take place and a few serotypes are circulating simultaneously and the virus is abundant in nasal discharge.

The control is the flu vaccination, antiviral drugs like receptor analog to prevent attachment, transcriptase inhibitors, RT inhibitors, Protease inhibitors and virions assembly.

Thus, as you can see that cold and flu are a not the same so next time if you have a either of these two think twice before you declare the virus!

8:32 AM

Thursday, January 1, 2009

Today one of us had a cold and we immediately thought about rhinovirus. So today we are going to talk and revise rhinovirus.

Rhinovirus is one of the genera from the largest virus family called Picornaviridae.
The Morphology is that there are naked virions, isometric nucleocapsid and there are common incomplete or empty capsids. The Picornaviridae genome contains an infectious genomic RNA, one linear (+) RNA, long untranslated region end of 5’ end “clover leaf” structure (IRES), single polyprotein of 2100-2400 aa and both ends are modified.

The Pathogenesis of Rhinovirus is that there will be an upper respiratory tract infection with short incubation (2-3 days) where endogenous IFN helps, there will also be locally synthesized IgA but titer decline with time and serum IgG persists for years and there are over 100 rhinoviruses.

The Symptoms that are seen are watery nasal discharge, congestion, sneezing and little or no fever.

The clinical lab diagnoses are virus culture, nasal washings, EIA and PCR.

The epidemiology is that it is present all throughout the year, a few serotypes circulating simultaneously and the virus is abundant in nasal discharge.

So what is the control? There is no vaccination as there are over 100 types and it will be a waste. What we can do is wash our hands, don’t touch our eyes or nose and we should sneeze into tissue and throw it away. Avoid people with cold and stay at home if you have a cold.

So now you should have understood about our common colds better right? Well, it’s amazing to know how far microbiology can go. By the way, when you get down with a type of rhinovirus, you will get immune to that type for life!

8:14 AM

Sunday, December 28, 2008

today we are going to talk abt hepatitis B.

Hepatitis B is a liver disease caused by the hepatitis B virus (HBV). It ranges in severity from a mild illness, lasting a few weeks (acute), to a serious long-term (chronic) illness that can lead to liver disease or liver cancer.
Transmission: Contact with infectious blood, semen, and other body fluids from having sex with an infected person, sharing contaminated needles to inject drugs, or from an infected mother to her newborn.
Vaccination: Hepatitis B vaccination is recommended for all infants, older children and adolescents who were not vaccinated previously, and adults at risk for HBV infection.

3:28 AM

Monday, December 22, 2008

Heys guys! Well todae we learnt a great deal about the differences between picornaviridae and orthomyxoviridae. A lot of us often used the word flu and cold interchangeable, but do u reallie know tat they is a huge differences between them??
Surprised??
Well dunt be as there is more to come….

Aniwae just to tok abt the differences, we as a group have sat down and discuss on ways to like summarized it all to like make it easier to like study for the exams and also make it easier for us to differentiate them. I’m sure you won’t wanna lose yr face in front of your frens rite??

Well, the differences are not only in the symptoms. There are also a lot of differences in the morphology, genome, pathogenesis, lab diagnosis, epidemiology and prevention.

well some pictures on picornaviridae:

well, here are some interesting articles related to the topic above:

that's about all...so check out for more information!!

3:52 AM

Sunday, December 21, 2008

In the classification of Retroviruses, the virus that attracts most researchers attention is none other than the Human Immuno Virus(HIV). Till now, there's no known cure available for AIDs.

HIV virus is under family of Lentivirus.

Spherical enveloped virion
2 copies linear plus sense single stranded RNA
Non tumour forming

Aids cause destruction of CD4 + T cells

Transmission through sexual contact, blood and blood products or during pregnancy.

Video below shows the HIV life cycle. If it does not appear, click the link below

http://www.youtube.com/watch?v=9leO28ydyfU

For more information on life cycle on HIV virus, You may visit this link below.

http://images.google.com.sg/imgres?imgurl=http://static.howstuffworks.com/gif/aids-hiv-anatomy.gif&imgrefurl=http://health.howstuffworks.com/aids2.htm&usg=__vYEJ47UQg2UrOoedCfB-iztRio0=&h=404&w=402&sz=57&hl=en&start=16&um=1&tbnid=SADbWJqc8nr6vM:&tbnh=124&tbnw=123&prev=/images%3Fq%3DHIV%26um%3D1%26hl%3Den%26sa%3DN

9:57 PM

Tuesday, December 16, 2008

hey guys!! well lets tok abt virology!!Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy. Virology is often considered a part of microbiology or of pathology. Virology is that branch of life science,which deals with the study of virus and virus-like agents,in terms of structure,classification,evolution,virulence and their culture. well, hope u guys uds now..hahs...well, ill let u noe more abt virology!!

2:10 AM