PBL blog 2 - Viruses part 2

In this post, I will be concentrating on 5 main viruses as a follow up on the previous post.

1. Chikungunya


Caused by: Alphavirus of the Togaviridae family. (1)

Transmission: Ades aegypti mosquito vectors (1)

Pathogenesis: Sylvatic cycle.


Chikungunya virus under scaning electron microscope. Picture taken from: http://www.flickr.com/photos/ajc1/1257163357/

Symptoms: Petechial (small red dot) or maculopapular (bumpy bumps) rash around the limbs and trunk. Polyarthritis resulting in debilitating pain causing contortions in affected joints, headache, slight photophobia (sensitivity to light), fatigue, nausea, vomiting and muscle ache. There are many other symptoms depending on age and severity of the disease. Note that the disease is similar to dengue. (2)







Women suffering from severe joint pains in a hunched position. Picture taken from : http://www.semp.us>
publications>biot_reader.php?BiotID=339



Suitable precaution: Avoid mosquito bites such as wearing long sleeves and long pants to cover the limbs and to treat clothes with permethrin or alternatively, use insect repellents.


2. SARS (Severe Acute Respiratory Syndrome)

Caused by: SARS coronavirus



<---- Sars coronovirus under scanning electron microscope. Picture taken from: http://pathmicro.med.sc.edu/graduate/corona-cdc.jpg


Transmission: Spread mainly by close person-to-person contact. When an infected person coughs or sneezes, droplets of mucus or saliva that contain the virus are sent through the air. Once these droplets land on the mouth, nose or eyes, an infection can occour.
Kissing, touching, sharing utensils for eating and drinking, or talking with an infected person is also a risk factor for infections. if you travel to countries with SARS. There is no treatment for SARS. Scientists are testing treatments and vaccines. (8)

Pathogenesis:

Week 1: Fever, muscle aches and other symptoms that generally improves after a few days.
Week 2: Patients experiences recurrance of fever, diarrhea and oxygen desaturation (characterised by breathing difficulties) and severe worsening of condition of the patient may occur. (6)


Damage of alveolar (lung) tissue due to SARs infection. Picture taken from http://pathmicro.med.sc.edu/virol/coronaviruses.htm

Week 3: Patients requires ventilatory support and some may develop end-organ damage and severe lymphopenia (abnormally low levels of lymphocytes, which is a type of white blood cells) resulting in death.

Symptoms: Patients are present with a high fever of > 38.0°C, including chills, headache, dizziness, rigors (shaking due to high fever), malaise (general feeling of discomfort), muscle aches.

Suitable precaution: Observe hygiene such as frequent washing of hands and avoid sharing of utensils.



Caring for a SARs patient in the ICU. Notice the attire of the clinicians and the pathogenecity of the virus. Picture taken from: http://www.bact.wisc.edu/themicrobialworld/SARS.html


3.Tick borne encephalitis

Caused by: Tick-borne encephalitis virus (TBEV) which is a member of the Flaviviridae family.

Transmission: Tick bites of the ixodes species

Pathogenesis: Ticks are the hosts and the reservoir of the virus. TBEV chronically infects ticks and is transmitted from larva to nymph to adult ticks. TBEV infects humans when tick bites during the peak period of april to november. (9)




Tick responsible for TBE. Picture taken from: http://www.hqusareur.army.mil/htmlinks/Press_Releases/2007/May2007/08May2007-01.htm


Symptoms: Asymptomatic for the first 2 weeks. Non-specific symptoms including fever, muscle aches, anorexia, headache, nausea and vomitting.

Suitable precaution: Vaccination and using insect repellents and protective clothing such as long sleeves, long pants and covered shoes.


4. Influenza (Flu)

Caused by: Family of Orthomyxoviridae viruses known as the influenza viruses.

Transmission: From infected bird droppings, coughing and sneezing of infected person, creating aerosols of the virus and contact with contaminated surfaces. (5)


<--- Model of the influenza virus. Picture taken from: http://www.3dscience.com/Resources/Influenza_Virus.php


Pathogenesis: Entry to host cells followed by binding of the host's columnar epithelial cells at the respiratory tract. Fusion with the cell's membrane and release of viral RNA which replicates within the nucleus, synthesizing structural and envelope proteins then releasing virions infecting neighbouring cells.

Symptoms: Fever, extreme coldness, sore throat, muscle pains, severe headache, coughing, weakness, fatigue, nasal conjestion, redden irritated watery eyes, coughing, sneezing and general discomfort.

Suitable precaution: Influenza vaccinations and observe hygiene.


5. Hepatitis A

Caused by: Hepatovirus hepatitis virus (HAV) (3)

Transmission: Contaminated food and water.

Symptoms: Nausea, diarrhea, fever, jaundice, fatigue, abdominal pain, loss of appetite and weight loss. (4)

Hepatitis virus under the scanning electron microscope. Picture taken from: http://zh.wikipedia.org/wiki/%E7%94%B2%E5%9E%8B%E8%82%9D%E7%82%8E

Suitable precaution: Vaccination and throughly cook food, drink boiled water and observe personal hygiene.



References:

1. Chikungunya: http://en.wikipedia.org/wiki>Chikungunya

2. Chikungunya Fever Fact Sheet :
http://www.cdc.gov>ncidod>dvbid>Chikungunya>chikvfact.htm

3. Hepatitis A: http://www.cdc.gov>ncidod>diseases>hepatitis>a>fact.htm

4. Hepatitis A: http://en.wikipedia.org/wiki>Hepatitis_A

5. Influenza: http://en.wikipedia.org/wiki>Influenza

6. SARs: http://www.sarsreference.com>sarsref>diag.htm

7. SARs: http://www.sarsreference.com>sarsref>prevent.htm

8. SARs: http://www.sarsreference.com>sarsref>trans.htm

9.Tick bourne encephalitis:
http://www.cdc.gov>ncidod>dvrd>spb>mnpages>dispages>TBE.htm



Yeng Ting
TG02