Sunday, 20 January 2008

Possible Viral diseases--->Part 2

1. O'nyong'nyong virus

Caused by: Alphavirus of the Togaviridae family
This virus is a small positive sense single stranded nonsegmented RNA virus that replicates in the cytoplasm of cells

Transmission: Anopheles funestus and anopheles gambrae mosquito. It is found in Ades aegypti mosquito vectors in Asia.

Pathogenesis: Sylvatic cycle. Meaning, ades aegypti mosquito bites the human skin and introduces the virus into the bloodstream.

Symptoms: Polyarthritis (arthritis at multiple areas of the joints), rash and low grade fever. Other symptoms that may not may not present includes eye pain, chest pain, lymphadenitis (lymph node inflammation) and lethargy.

Suitable precaution: Note that currently, there are no vaccines available. The best method in prevention is to 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. Chikungunya

Caused by: Alphavirus of the Togaviridae family which is similar to the o'nyong'nyong virus

Transmission: Ades aegypti mosquito vectors

Pathogenesis: Sylvatic cycle.

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.

Suitable precaution: Same as o'nyong'nyong virus.


3. SARS (
Severe Acute Respiratory Syndrome)

Caused by: SARS coronavirus

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.


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.
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.


4.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.

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.


5. West Nile Fever

Caused by: West nile virus of the flaviviridae family

Transmission: Bites of the Culex quinquefasciatus (southeast asia), Culex pipiens (in the US) and Culex tarsalis (in the middle east and europe) mosquito.

Symptoms: There are 3 different effect of the virus on humans.

(a) Serious symptoms -----> neuroinvasive disease known as meningitis or encephalitis where patients may experience
a decreased level of consciousness which may develop into near-comatose stage. Symptoms includes high fever, stiff neck, headache, stupor, disorientation, coma, tremors, convulsions, muscle weaknes, loss of vision, numbness of the limbs and paralysis.

(b) Mild symptoms -----> patient experiences a mild febrile (fever) syndroms known as West Nile Fever. Sypmtoms includes fever, headache, body aches, nausea, vomitting, swollen lymph nodes and rashes appearing around the trunk area.

(c) Asymptomatic

Suitable precaution: Same as o'nyong'nyong virus and chikungunya.


6. 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.

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.


7. Hepatitis A

Caused by: Hepatovirus hepatitis virus (HAV)

Transmission: Contaminated food and water.

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

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


Yeng Ting

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