Now that we understand what viruses are and how they work, let’s take a look at some of the most common types of viruses affecting us today:
Cold or Flu?
Do you know the difference between the flu and the common cold? How often do we claim “flu” as our diagnosis, but it is really?
The most common viruses that affect humans are rhinoviruses. These guys live in the upper respiratory tract and are responsible for causing the common cold. There are 99 different types of rhinoviruses, and they are among the smallest viruses in existence. They are RNA viruses, and have a protein coat (capsid) and are covered with proteins on the outside.
Rhinoviruses are transmitted via person-to-person contact, and by interaction with fomites. (Nerd Tip: If you haven’t get watched it, Contagion is a great movie about how disease outbreaks affect us in this century). Fomites refer to contaminated surfaces, and can include doorknobs, tabletops, faucets…pretty much everything we touch. . Symptoms of the common cold are sore throat, runny nose, nasal congestion, sneezing and cough, muscle aches, fatigue, malaise, headache, muscle weakness, or loss of appetite. Sounds familiar?
Influenza on the other hand is a much more serious disease, caused by the influenza virus, or the group of Orthomyxoviridae. While the common cold generally resolves on its own, influenza outbreaks can results in the deaths of tens of millions of people. There are seven types of influenza virus, with influenza A, B and C being the groups that attack humans. Influenza viruses are also RNA viruses, generally spherical in shape with 500 distinct spike-like surface projections on its envelope.
Each Influenza virus contains different subtypes, which came about when the virus mutated to a new form. For example, the Influenza V virus has 3 subtypes that are currently in circulation: H1N1 (Spanish Flu/2009 “Swine Flu” Outbreak), H1N2, H3N2 (“Hong Kong Flu”). Human flu symptoms usually include fever, cough, sore throat, muscle aches, conjunctivitis and, in severe cases, severe breathing problems and pneumonia that may be fatal.
Vector-Borne: Dengue & ZikA
Both dengue fever and ZikA are mosquito borne viruses transmitted by the Aedes aegypti mosquito. Dengue virus is an RNA virus that can prevent the functioning of your immune system that Is necessary to fight off the disease. There are 47 strains of the dengue virus. Dengue fever can cause high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash.
The ZikA virus is an RNA virus that has recently caused a new pandemic in some parts of the world. The ZikA virus is found in the mosquito’s saliva, so when the mosquito bites, some of the ZikA virus is introduced into skin cells and the blood stream. Zika usually causes no or only mild symptoms, similar to a very mild form of dengue fever. However, ZikA can be transmitted from mother to foetus, and can result in microcephaly, severe brain malformations, and other birth defects.
HIV & HPV
The human immunodeficiency virus (HIV) is a retrovirus that causes HIV infection and AIDS. Retroviruses are able to insert themselves into your cells and use its own machinery to read the genetic information on the virus and create a copy that integrates into your DNA. This is why the HIV virus is so hard to treat. The HIV virus is generally spherical on the outside, with a cone shaped capsid inside storing the genetic material. It also contains proteins on the outside of the viral envelope that give it a sort of spiky appearance.
HIV also has a very high mutation rate, which has given it much genetic variability – many many different strains and subtypes exist, making it much harder to design a treatment for all infections. The HIV virus is transmitted via bodily fluids such as blood, semen, vaginal fluid and breast milk. By attacking your immune system, it directly attacks the defence system of your body, crippling your ability to fight off diseases.
The human papillomavirus is a small DNA virus that causes HPV infections. HPV infections cause genital warts and precancerous lesions, and is generally spread by sustained direct skin-to-skin contact. So obviously, during sex is pretty likely. HPV is the most common sexually transmitted infection globally, but luckily the HPV vaccine prevents the most common types of HPV infection.
Over 170 types of HPV have been detected, of which above 12 of these are considered “high risk” because they can cause cancer. The HPV virus cannot attach to live cells, so instead it waits till you get a tiny little cut or some trauma deep within your skin, and it moves through your skin membranes.