chikungunya virus (RNA virus)

What is HIV and AIDS?

HIV stands for Human Immunodeficiency Virus. HIV is a virus that takes over certain immune system cells to make many copies of itself. HIV causes slow but constant damage to the immune system.

AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is the condition diagnosed when there are a group of related symptoms that are caused by severe HIV infection. AIDS makes the body vulnerable to life-threatening illnesses called opportunistic infections.

How does HIV affect the body?

Normally, the human immune system is the body’s protection against bacterias, viruses, etc.; it is like a coat of armor. When HIV enters the body, it starts poking holes in the armor. Eventually, the armor becomes very weak and unable to protect the body. Once the armor is very weak or is gone, the person is said to have AIDS. An AIDS diagnosis is generally made when either the body's protective T-cells drop below a certain level, or the HIV-positive individual begins to experience opportunistic infections. An opportunistic infection is an infection that would not normally affect an otherwise healthy person. Oftentimes, it's these infections that are the cause of illness or death in HIV-positive individuals - not the virus itself. If people do not get any treatment for HIV disease, it takes an average of 8-10 years to progress from HIV to AIDS.

How is HIV transmitted?

HIV is transmitted through four body fluids: blood, semen, vaginal fluid, and breast milk. In order to pass HIV from one person to another, HIV-infected fluid from one person needs to get into the bloodstream of another person. HIV is usually transmitted through sharing needles, unprotected anal, vaginal, and sometimes oral sex, and from mother to infant before or during delivery or while breastfeeding.

**Special Note for HIV-Positive Mothers:

In developed countries like the U.S., formula feeding is strongly recommended over breastfeeding for babies of HIV-positive mothers. Whether choosing breastfeeding or formula, there should be little or no switching between the two, as doing so could put the child at a higher risk of contracting HIV, since baby formula can be harsh and weaken the lining of a baby's stomach, giving a path for HIV to enter the baby's bloodstream.

How can I prevent myself from contracting HIV?

Becoming educated about HIV and understanding how it is transmitted is the first, and perhaps most important way to prevent the spread of HIV. It is essential for people to make informed decisions about the level of risk they are willing to take, based on what is realistic for them.

Abstaining from sex and needle sharing is the most effective way for people to protect themselves from HIV and other sexually transmitted diseases. However, abstinence is not a realistic option for everyone.

Safer Sex

When abstinence is not an option, the proper use of barrier protection such as latex or polyurethane condoms (male or female), with a water based lubricant*, is the next best thing for vaginal or anal sex.

An HIV virus attaching to a host cell





Coronaviruses being absorbed into a host cell. The plasma membrane is budding inward, and will release the viruses inside the cell




Hepatitis A virus reproducing inside a cell



Electron micrograph of a respiratory syncytial virus (RSV) in in the process of budding at the cell membrane



A liver cell killed by infection with the hepatitis C virus

what is hepatitis C?

There are at least six viruses known to cause liver disease: hepatitis A, B, C, D, E, and G, which vary in their severity and characteristics. Hepatitis C can lead to serious, permanent liver damage, and in many cases, death.

As a result, most Hepatitis C infections (80-90%) become chronic and lead to liver disease, including cirrhosis (scarring of the liver tissues) and liver failure. Hepatitis C infection is typically mild in its early stages, and it is rarely recognized until it has caused significant damage to the liver. The cycle of disease from infection to significant liver damage can take 20 years or more.

Blood transfusions account for nearly 10% of all cases of Hepatitis C. Prior to 1990, there were no tests for hepatitis C in donated blood, and the risk of infection was between 8 and 10%. Since 1993, risk has been negligible.

The Hepatitis C Epidemic

In June 2009, the WHO declared Influenza A (H1N1) a global pandemic. This new strain now exists in many communities all over the world.

As this is a new strain of virus, most people will not have resistance, and it can potentially spread quickly and infect a large proportion of the population in a short period of time.

While the drugs Tamiflu® and Relenza® can be used to treat a H1N1 infection, there is currently no vaccine available.

Causes

Human-to-human transmission of Influenza A (H1N1) has been occurring all over the world. Flu can be spread when a person coughs, sneezes or speaks. The flu viruses are transmitted into the air through droplets that can be inhaled by many other people. When these viruses enter the nose, throat or lungs of an infected person, they begin to multiply, causing symptoms of flu.

Influenza A (H1N1) infection is highly contagious. People with an infection may be able to spread the flu virus a day before the symptoms appear and throughout the period that he/she is ill.

Symptoms of Influenza A(H1N1)

Just like the seasonal flu, Influenza A (H1N1) infection in humans can vary in severity from mild to severe. Signs and symptoms of infection may include the following:

• High fever (Temperature > 38°C)
• Cough
• Muscle pains
• Sore throat
• Fatigue or tiredness
• Headache
• Nausea
• Vomiting or diarrhea

See your family doctor if you have any of the above symptoms.

Most cases of Influenza A (H1N1) are mild and self-limiting and patients recover. However, there are several groups of individuals are at high-risk of developing complications from this strain. These high-risk groups include:

• Persons aged 65 years and older
• Children under five years of age
• Those with chronic metabolic disease (including diabetes mellitus), chronic pulmonary or heart disease
• Those with medical conditions such as cancer on active treatment, on organ transplant dialysis, or immunosuppression (including immunosuppression caused by medications or by HIV)
• Children and teenagers less than 18 years who are receiving long-term aspirin therapy
• Pregnant women

If you are pregnant, undergoing cancer treatment or dialysis you should consult your primary care specialist. All other groups should go to a Pandemic Preparedness Clinic (PPC), polyclinic or their primary care doctor.

Call 995 if you experience the following warning signs or if your symptoms worsen:

• Difficulty in breathing or chest pain
• Purple or blue discolouration of the lips
• Severe and persistent vomiting
• Deterioration of symptoms since the onset of illness
• Flu-like symptoms improve but then return with fever and worse cough
• Signs of dehydration such as dizziness when standing, the absence of urination of lack of tears when children cry
• Fits
• Loss of appetite
• Less responsive than normal, drowsy or becomes more confused

Treatment of Influenza A(H1N1)

Anti-Viral Drugs
There are anti-viral medications available to treat people who are infected. Anti-viral medications such as Tamiflu® or Relenza® fight against the influenza viruses from reproducing in the body.

These medications, when taken early in the course of infection (within 2 days of the appearance of symptoms) may:

• Reduce the severity of the infection with faster recovery from the illness.
• Prevent serious flu complications.

In most cases, laboratory testing to confirm infection with Influenza A (H1N1) is not needed before starting treatment. Doctors will exercise clinical judgement in prescribing anti-viral drugs on a case-by-case basis taking into account of patient’s risk of developing influenza-related complications, prevalence of infection in the community and the risks and benefits of treatment. As with any other medications, there are potential side-effects related to the use of Tamiflu.

Vaccinations
The current seasonal flu vaccine gives little (if any) protection against the new Influenza A (H1N1) strain. There is no vaccine available for this new strain of H1N1 virus yet. Vaccine manufacturers are currently in the process of producing and testing a vaccine for this new strain.

Prevention

Since the illness occurs through direct contact with infectious material and respiratory secretions, it is important to practice good personal hygiene. Take these everyday steps to protect your health:

Cover Your Nose and Mouth

• With a tissue when you cough or sneeze and dispose the tissue properly in the trash after use.

Wash Your Hands

• Regularly and thoroughly with soap and water
• Before and after preparing food
• After going to the toilet
• Before and after eating
• After blowing your nose
• After using your hand when coughing or sneezing

Contain the Spread of Flu

• Use a serving spoon when sharing food from a common dish.
• Do not share personal items such as toothbrushes and towels.
• Avoid touching your eyes, nose or mouth.
• Consider wearing a mask and avoid crowded places if you are in a high-risk group.
• Stay at home and do not go to work or school if ill.
• Head to your nearest Pandemic Preparedness Clinic (PPC) if you have flu like symptoms.

Build Up Your Immunity

• If you are a smoker, quit smoking. It harms you and your family.
• Take more fruit and vegetables. Fruit and vegetables are the most power-packed combination of nutrients your body needs for good health.
• Drink the equivalent of 8 glasses of fluid daily.
• Engage in 30 minutes of moderate intensity physical activity on 5 or more days a week.
• Learn to relax and rest.

Keep Your Environment Clean

• Do not throw leftover food on the floor or in the open.
• Do not leave food in common areas for stray animals.
• Do not spit on the floor and common areas.
• Throw used masks, tissue or litter into rubbish bins.

If you are living with someone who is infected

• Observe good personal hygiene.
• Do not have meals together with the ill person as masks have to be removed during meals.
• Wear a surgical mask and remain at a distance of at least 2 metres from one another if you need to communicate with the ill person.
• Maintain good ventilation at home (e.g. keeping windows open in toilets, kitchens and rooms)
• Be socially responsible by limiting contact with someone outside your household. When you need to go out, consider wearing a mask and avoid crowded places.

If you are looking after someone who is infected

• Wear a surgical mask.
• Clean your hands with soap and water (or an alcohol-based hand rub) after you have touched the infected person, soiled linens or laundry.
• Be alert and call for help when the infected person’s symptoms deteriorate of if the symptoms worsen.
• If you are pregnant you should not be looking after someone who is infected as you are at increased risk of flu-related complications.

indirect ELISA
sandwich ELISA(also known as antibody-antigen reaction)
reverse ELISA
competitive ELISA

Most common type of ELISA is the antibody-antigen

BACKGROUND INFORMATION

Viruses are infectious agents with both living and nonliving characteristics.

1. Living characteristics of viruses

a. They reproduce at a fantastic rate, but only in living host cells.

b. They can mutate.

2. Nonliving characteristics of viruses

a. They are acellular, that is, they contain no cytoplasm or cellular organelles.

b. They carry out no metabolism on their own and must replicate using the host cell's metabolic machinery. In other words, viruses don't grow and divide. Instead, new viral components are synthesized and assembled within the infected host cell.

c. The vast majority of viruses possess either DNA or RNA but not both.

Baltimore classification

Class I: Double stranded DNA viruses

Class II: Single stranded DNA viruses

Class III: Double stranded RNA viruses

Class IV & V: Single stranded RNA viruses

Class IV: Single stranded RNA viruses - Positive (+) sense

Class V: Single stranded RNA viruses - Negative (-) sense

Class VI: Positive (+) sense single stranded RNA viruses that replicate through a DNA intermediate

Class VII: Double stranded DNA viruses that replicate though a single stranded RNA intermedia

• Phylum Vira (divided into 2 subphyla)

• Subphylum Deoxyvira (DNA viruses)

• Class Deoxybinala (dual symmetry)

• Order Urovirales

• Family Phagoviridae

• Class Deoxyhelica (Helical symmetry)

• Order Chitovirales

• Family Poxviridae

• Class Deoxycubica (cubical symmetry)

• Order Peplovirales

• Family Herpesviridae (162 capsomeres)

• Order Haplovirales (no envelope)

• Family Iridoviridae (812 capsomeres)
• Family Adenoviridae (252 capsomeres)
• Family Papiloviridae (72 capsomeres)
• Family Paroviridae (32 capsomeres)
• Family Microviridae (12 capsomeres)

• Subphylum Ribovira (RNA viruses)

• Class Ribocubica

• Order Togovirales

• Family Arboviridae

• Order Lymovirales

• Family Napoviridae
• Family Reoviridae

• Class Ribohelica

• Order Sagovirales

• Family Stomataviridae
• Family Paramyxoviridae
• Family Myxoviridae

• Order Rbadovirales

• Suborder Flexiviridales

• Family Mesoviridae
• Family Peptoviridae

• Suborder Rigidovirales

• Family Pachyviridae
• Family Protoviridae
• Family Polichoviridae