Wednesday, January 23, 2008

 

Virus

Virus is a sub-microscopic infectious agent requires a host to outside cell. [1] Each viral particle, or virion, consists of genetic material, DNA or RNA, within a protective protein coat called a capsid. [1] The capsid shape varies from simple helical and icosahedral (polyhedral or near-spherical) forms, to more complex structures with tails or an envelope.

When a virus infect a host cell, several changes occurs. [1] For example,
- death of cell due to inhibition of macromolecule synthesis
- fusion of cells to form multinucleated cells
- malignant transformation
- no morphological/functional changes

Pathogenesis in the infected patient involves [1]
- transmission of virus and its entry into host
- replication of virus (viral proteins) and damage to cells (lysis)
- immune responses against virus
- persistence of virus (unable to be remove from the body even after immune responses has been mount)

Virus can be transmitted from person-person or animal-person. [2] Person-person transmission can be due to exposure to respiratory secretion, saliva, blood (transfusion, sharing of needles), semen, fecal contamination of water or food. [1] This is called horizontal transmission. Person-person transmission can also be from maternal to fetal/child across the placenta or during breast-feeding. This is called vertical transmission. Animal-human transmission occurs directly when infected animal is exposed to human while indirect transmission occurs through the bite of an insect vector e.g. mosquito. [1]

Viral infections in human and animal hosts usually result in an immune response and disease.[5] Viruses are usually eliminated by immune responses in the body. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat life-threatening infections. Vaccines that produce lifelong immunity can prevent virus infections e.g. poliomyelitis.
Here are some of the viruses that have have shortlisted


Parainfluenza virus [2, 4]
Epidemiology: Parainfluenza 1, 2, 3 & 4, with Parainfluenza 1& 2 being commonly during autumn and Parainfluenza 3 infections occur throughout the year.

Transmission: Inhalation of large respiratory droplets, person-person contact. Re-infection occurs throughout life as body’s immunity to it is short.

Signs and symptoms: cold-like syndrome, croup, cough, chest pain

Causes: bronchiolitis, bronchitis, upper respiratory tract infections and pneumonia.

Modes of control: No vaccine is yet available for routine use







http://www.yahoo.com/ > Image > Parainfluenza virus




Influenza A virus [2, 4, 8]
Influenza A virus infects multiple species. Wild aquatic birds are the nature host to a variety of influenza A viruses. The virus is then transmitted to other species and causing devastating outbreaks in domestic poultry or give rise to human influenza infections. There are several types of influenza A virus:

· H1N1 caused "Spanish Flu."
· H2N2 caused "Asian Flu."
· H3N2 caused "Hong Kong Flu."
· H5N1 is a pandemic threat in 2007–8 flu season; Avian Flu
· H7N7 has unusual zoonotic potential.
· H1N2 is endemic in humans and pigs.
· H9N2, H7N2, H7N3, H10N7


Avian Flu [2, 4, 8, 9]
Epidemiology: Bird populations especially in Southeast Asia

Transmission: Avian Flu caused by H5N1 virus infects bird populations. The infected birds then spread its infection through saliva, nasal secretion, blood and droppings to other animals and humans with extensive physical contact e.g. direct contact with these bodily fluids or through contact with surfaces contaminated with them

Causes: Avian Flu

Signs and symptoms: Fever, cough, sore throat, pneumonia, breathing difficulties and sometimes diarrhea.

Modes of control: H5N1 Vaccines but they are not always effective due to continuous mutation of the virus, culling of infected bird population, protection used when dealing with droppings.







http://www.yahoo.com/ > Image > Avian Flu Virus



Influenzavirus B [2, 4, 8]
Epidemiology: Worldwide occurrence: epidemics are local and pandemics are worldwide

Transmission: Spread by inhalation of small aerosol droplets expelled for infected individual, saliva, blood, feces, nasal secretion.

Causes: Pneumonia, lower respiratory infection, acute influenza infection in adults and complications influenza virus infections.

Signs and symptoms: Fever, sore throat, muscle aches, coughing, nausea, vomiting

Modes of control: amanatdine, rimantadine etc, killed vacinne contains predicted yearly strains of
influenza A & B virus



SARS coronavirus [6, 8]
Epidemiology: Most number of SARS cases occurred in People’s Republic of China, Hong Kong, Taiwan, Singapore and Canada with 7%, 17%, 14% & 17% fatality respectively

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, enter the nose or eyes, an infection can occur. However, the airborne spread of SARS does not seem to be a major route of transmission. In addition, kissing, touching, sharing utensils for eating and drinking, or talking with an infected person are also a risk factor for infections. The presence of virus in the stool also suggests the possibility of oral-fecal transmission

Causes: Severe acute respiratory syndrome (SARS)

Signs and symptoms: Fever, Chills, muscle soreness, headache and a general feeling of discomfort also are common. Severe pneumonia, leading to an insufficient amount of oxygen in the blood (hypoxemia) can also occur
Modes of control: Wash your hands frequently with soap and hot water, Cover your mouth and nose when sneezing and coughing. Use soap and hot water to wash the utensils, towels, bedding and clothing of someone with SARS. Don't use these items yourself until they're clean.







http://www.yahoo.com/ > Image> SARS coronavirus



Alphavirus [2, 4, 5]














Chikungunya Virus (It is a virus under the category of alphavirus)
Epidemiology: The disease was first recognized in Eastern Africa in the 1950s. Outbreaks were also reported in Malaysia, India, Sri Lanka and Indonesia in 2006. In 2008, 6 infections caused by chikungunya virus were reported in Singapore.

Transmission: Chikungunya is spread by the bite of an infected mosquito. The main vector is mosquito Aedes aegypti. Other mosquito likes Aedes albopictus and Culex can also transmit the disease. Mosquito becomes infected when they feed on a person infected with chikungunya. Monkeys and other wild animals may also serve as a reservoir of the virus. Infected with mosquito can then spread the virus to other humans when they bite. There is no direct person to person spread.

Causes: Chikungunya fever

Signs and symptoms: Chills, fever, headache, vomiting, fatigue, nausea, rash and muscle and joint pain, some patients may also develop a rash affecting the trunk

Modes of control: The most effective means of prevention are those that protect against any contact with the disease-carrying mosquitos. These include the usage of insect repellents with substances like DEET (Diethyl-3-methylbenzamide), icaridin (also known as picaridin and KBR3023), PMD (p-menthane-3, 8-diol, a substance derived from the lemon eucalyptus tree), or IR3535. Wearing bite-proof long sleeves and trousers also offers protection. In addition, garments can be treated with pyrethroids, a class of insecticides that often has repellent properties. Vaporized pyrethroids (for example in mosquito coils) also have a certain special repellency.
Of all the alphavirus, Chikungunya virus is the only virus in this category that is distributed in South East Asia (Indonesia), thus it is the most probably virus from this category to infect soldiers who are training in the forest of Indonesia








http://www.yahoo.com/ > Image > Chikungunya Virus




Flavivirus [2, 4, 5]













Epidemiology: Aedes mosquito, which carries dengue and yellow fever, is found in urban areas, pools of water and jungles while Culex mosquito is found in the forest, urban areas. Disease is more common in summer.

Transmission:









Signs and symptoms: Flu like symptoms (chills, fever, rash, aches), dengue yellow fever

Mode of control: Mosquito breeding sites should be eliminated. Live attenutaed vaccines are available for yellow fever virus


Adenovirus [2, 4, 10]
Epidemiology: Worldwide endemic, frequent observations in transplant patients and military recruits.

Transmission: Adenovirus can be human-to-human transmission mainly by fecal-oral or respiratory route, by fingers, by fomites (including towels and medical instruments). In addition, close interaction among people such as military barracks promotes the spread of the virus

Causes: Adenoviral pneumonia, due to adenovirus serotype 4 & 7, is a complication of acute respiratory diseases in military recruits, conjuctivitis

Signs and symptoms: Fever, cough, pharynitis
Modes of control: Live vaccine for serotype 4 and 7 are avaliable for military use






http://www.yahoo.com/ > Image > Adenovirus


Enterovirus [2, 3, 5]
Polioviruses (causes poliomyelitis)
Coxsackieviruses (A and B) (causes hand-foot-mouth disease)
Echoviruses
Enteroviruses
e.g.
Enterovirus 70

Epidemiology: Worldwide distribution except for poliovirus which has been eradicated, only a few random cases occurs.
Polioviruses – humans, ape, monkeys
Coxsackieviruses – human, most common in summer and autumn
Echoviruses – human
Enteroviruses - human

Infections most common in early childhood but adults get infected when their bodies do not possess the immunity against the enterovirus invading.

Transmission:
Transmitted by oral-fecal route, poor hygiene, inhalation of aerosol, ingestion via contaminated food and water, contact with infected hands and fomites, poor sanitation, crowded living conditions

Causes:
Polioviruses - poliomyelitis
Coxsackieviruses (A and B), Echoviruses and Enteroviruses - causes hand-foot-mouth disease, herpangina,aseptic meningitis, myocarditis and can cause serious disease especially in infants and the immunocompressed.
Enterovirus 71 causes respiratory infection.

Signs and symptoms: Rash disease, respiratory diseases, undiferentiated fever

Modes of control: Practice good hygiene, improve living condition

Poliovirus is an extinct disease due to vaccination except in undeveloped countries, in addition, it is manifested since young, the army soldiers are unlikely to be infected by it.


Molluscum contagiosum [1, 3, 4]
Epidemiology: Worldwide distribution.

Transmission: Transmitted by direct contact with infected human e.g. sexual contact, wrestling, or sharing of fomites e.g. towel, bed, clothing.

Signs and symptoms: skin lesion most commonly on trunk, genitalia and proximal extremities.

Causes: DNA poxvirus Molluscum contagiosum virus. There are 4 types of MCV, MCV-1 to -4, with MCV-1 being the most prevalent and MCV-2 usually seen in adults.

Modes of control: Hygiene - no sharing of baths and articles of clothing (towels), no scratching of lesion, bandage bumps.






http://www.yahoo.com/ > Imgae > Molluscum contagiosum



Bunyaviridae [2, 4]














Epidemiology: Common during summer. Found in South America, Southeast Asia, southeastern Europe and Africa.

Transmission: Transmitted by infected mosqutio, or ticks to vertebrates. The animal then becomes the resvoirs for the virus which in turn infect human. Also, humans get infected when they enter the environment of insect vector.

Signs and symptoms: Febrile illness and rash, headache, vomitting

Causes: Hantavirus pulmonary syndrome, Hemorrhagic fever

Mode of control: Elimination of vector or vector’s habitat






http://www.yahoo.com/ > Image>Bunyavirus







http://www.wikipedia.com/ > Hantavirus > Image




Hepatitis [2, 4, 5, 11]















Hepatitis A and E [2, 4, 5, 11]
Epidemiology: Worldwide, most common in tropical and subtropical regions.

Transmission: Fecal-oral route, direct contact with contaminants e.g. uncooked food, water, contact with infected individual e.g. sharing of food, drinks.

Signs and symptoms: Fever, loss of appetite, nausea, headache, pain in abdomen

Causes: Hepatitis A, Hepatitis E

Mode of control: Vaccination, good hygiene, consume thoroughly cooked food and water.

Considering that the soldiers are not exposed to blood products or any transfusion process, Hepatitis B, C and D are not possible. The lack of clean food and water in the jungle could have caused Hepatitis A and/or E infection is the soldiers.










http://www.yahoo.com/ > Image> hepatitis C





Rabies [2, 12]
Epidemiology: Animal reservoir e.g. foxes, bats, racoons. Most commonly found in Asia, Africa and South America.

Transmission: Spread from animals especially wild animals to human, Inhalation of aerosolized virus, saliva bite by a rabid animal.

Signs and symptoms: Fever, malasie, itching at the site of the bite, fear of water (hydrophobia).

Causes: infection to central nervous system (especially brain)

Modes of control: Avoid contact with wild animals as they are not vaccinated, immediate washing of wound with soap, detergent or other substances which inactivate the virus, Instill anitrabies serum with the adminstration of huamn rabies immunoglobulin (HRIG)








http://www.yahoo.com/ > Image > Rabies virus


Rhinovirus [2, 3, 4]
Epidemiology: occurs worldwide with high prevalence during winter

Transmission: crowding and close contact favors transmission via respiratory route.

Causes: chronic bronchitis, sinusitis

Sign and symptoms: coryza (inflammation of nasal membrane), fever (however not common in adults)

There is likelihood for soldiers to be infected with rhinovirus as it is transmitted by crowding and close contact, all these are common occurrence in the barrack.








http://www.yahoo.com/ > Image > rhinovirus



Human Immunodeficiency Virus (HIV) [2, 5]
Epidemiology: occurs worldwide

Transmission: Sexual contact, blood, maternal to fetal, breast milk.

Causes: HIV, other opportunistic infections as HIV-infected individual are immunocompromised

Sign and symptoms: flu-like symptoms after 2 weeks of manifestation

Assuming the soldiers visited the neighboring villages and had sexual contact/blood contact with an infected individual, there is a high chance that they are infected with HIV. However, if the soldiers had not venture out of their barrack and the jungle, the likelihood of them infected with HIV is very low as an HIV-infected individual would have been detected during their military health screening.






http://www.yahoo.com/ > Image > aids HIV virus



Norovirus [2, 4, 5]
Epidemiology: Worldwide, all ages

Transmission: faecally contaminated food or water, person-to-person transmission

Causes: stomach flu, gastroenteritis

Sign and symptoms: nausea, vomiting, diarrhea, weakness, fever.

Virus can be transmitted when contaminated food and water has been consumed, the likelihood increases when food/water is not thoroughly cooked. In army, due to large amount of food required to prepare and the lack of fire source during jungle warfare, food/water may not be thoroughly cooked.







http://www.yahoo.com/ > Image> Norovirus

Astrovirus [2, 3, 5]
The genus "Astrovirus" within the familiy of Astroviridae is divided into eight human species:
- human astrovirus 1 (HAstV-1) - human astrovirus 2 (HAstV-2) - human astrovirus 3 (HAstV-3) - human astrovirus 4 (HAstV-4) - human astrovirus 5 (HAstV-5) - human astrovirus 6 (HAstV-6) - human astrovirus 7 (HAstV-7) - human astrovirus 8 (HAstV-8)

Epidemiology: All ages especially the young and elderly. Adults in military barracks are most likely to develop the disease due to poor hygiene control.Worldwide endemic, common in tropical with rainy season

Transmission: contaminated food and water

Causes: gastroenteritis

Sign and symptoms: Diarrhea, vomiting, pain in stomach, dehydration

Virus can be transmitted when contaminated food and water has been consumed, the likelihood increases when food/water is not thoroughly cooked. In army, due to large amount of food required to prepare and the lack of fire source during jungle warfare, food/water may not be thoroughly cooked.


Filovirus [2]
There are two genera: the Ebola virus and Marburg virus. These viruses cause viral hemorrhagic fevers, characterized by bleeding and coagulation abnormalities, often leading to death. Natural reservoir of both the Marburg virus and the Ebola virus appears to be zoonotic. Infected individual symptoms may be mistaken for influenza, malaria, typhoid fever.


Marburg Virus [2]
Epidemiology: Africa, commonly transmitted by bats especially fruit bats

Transmission: disease is spread through bodily fluids, including blood, excrement, saliva, and vomit

Causes: Marburg haemorrhagic fever.

Sign and symptoms: Early stage: fever, headache and myalgia maculopapular rash present on the trunk. Later-stage: is acute and causes jaundice, pancreatitis, weight loss, delirium and neuropsychiatric symptoms, haemorrhaging, hypovolemic shock and multi-organ dysfunction, with liver failure.


Ebola Virus [2]
Epidemiology: Africa, commonly transmitted by animals e.g. monkeys, bats especially fruit bats

Transmission: airborne, from infected animals to human, human to human transmission is rare.

Causes: Ebola haemorrhagic fever.

Sign and symptoms: Early stage: high fever, severe headache, muscle, joint, or abdominal pain, severe weakness and exhaustion, sore throat, nausea, and dizziness. Later-stage: diarrhea, dark or bloody feces, vomiting blood, red eyes due to distention and hemorrhage of sclerotic arterioles, petechia, maculopapular rash, and purpura.

During jungle warfare, the soldiers are exposed to wide variety of wild animals e.g. monkey and bats. The animals may be infected with the virus and transmit it to the soldiers thus infecting them. Therefore, the occurrence of filovirus infection is rather high.


References

1. Levinson, W. (2006). Review of Medical Microbiology & Immunology. San Francisco, California: Lange Medical Books/McGraw-Hill publishing company
2. Murray, P.R. (2002). Medical Microbiology. St. Louis, Missouri: Mosby Inc.
3. Elliott T., Hasting M. and Desselberger U. (1997). Lecture Notes on Medical Microbiology. Blackwell Science,Oxford
4. Walker, T.S. (1998). Microbiology. Philadelphia, Pennsylvannia: W.B Saunders Company
5. Brook G. F., Butel J. S. and Morse S. A. (1998). Jawetz, Melnick & Adelberg’s Medical Microbiology. Prentice Hall International Inc., United States of America
6. http://www.mayoclinic.com/ > search> SARS
7. http://www.sarsreference.com/
8. http://www.wikipedia.org/ > search influenza
9. http://www.wikipedia.org/ > search > avian flu
10. http://www.wikipedia.org/ > search > adenovirus
11. http://www.wikipedia.org/ > search hepatitis
12. http://www.wikipedia.org/ > search > rabies

Done by:
Eugene and Phuiyuen, TG02

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