In medicine, the term contagious disease is used to define an infectious disease (caused by the propagation of a virus, a parasite or a bacterium) that is transmitted from one individual to another. These diseases are very numerous, and can be transmitted :
- Either directly: via the droplets contained in the cough, by touching the unwashed hands of a contaminated person, by kissing a sick person, through sexual intercourse, etc.
- Or indirectly: by touching an object handled by a contaminated person and on which he or she has left bacteria, by sharing an object soiled by the virus, by eating contaminated food, and even through insects.
Even though many contagious diseases are benign, it is still best to avoid them! To do so, in case of epidemic or contagious period, it is simply advised to avoid any potentially contaminating contact, and to adopt an impeccable hygiene.
1. Hepatitis B
Hepatitis B is a viral disease that is transmitted through the HBV virus. Once the hepatitis B virus has entered a person’s body, it attacks the liver by multiplying on the liver cells, the hepatocytes, which leads to severe inflammation (which can lead to destruction).
Hepatitis B can be transmitted from one individual to another:
- during sexual intercourse,
- through contaminated material (injections, tattoos, etc.),
- during risky blood transfusions,
- during childbirth (a mother who transmits it to her child).
Even if hepatitis B is a contagious and infectious disease that can be treated and that there is a vaccine, it is a disease that can in some cases be fatal; it is then called fulminant hepatitis.
2. Hepatitis C
While hepatitis B is transmitted via the HBV virus, the infectious agent responsible for hepatitis C is a member of the flavivirus family, HCV. Like hepatitis B, this contagious disease represents one of the most dangerous forms of viral hepatitis: approximately 2700 deaths per year are due to hepatitis C.
Hepatitis C can be transmitted from one individual to another:
- during sexual intercourse (in a minority of cases),
- through poorly or unsterilized equipment (acupuncture needles, tattoos, etc.), even if these cases are nowadays quite rare… at least in industrialized countries,
- by blood transfusions (same remark as for the previous point).
Influenza is an infectious viral disease that often strikes in winter (despite the many prevention campaigns and possible vaccines!). It is caused by a virus called influenzavirus, which attacks the respiratory system and causes, among other things: a great feeling of fatigue, fever, muscle aches, headaches, chills, dry cough, sneezing and runny nose.
Influenza is a highly contagious disease, which is transmitted from one individual to another :
- by direct contact (handshake, peck on the cheek, kiss, etc)
- or by indirect contact, by touching an object (pen, door handle, computer keyboard, etc.) that the infected person has touched before. Yes: the flu virus is very resistant and can survive outside the body for several hours!
Along with influenza, rhinopharyngitis is another contagious winter disease that involves a virus that attacks the upper respiratory tract. In terms of symptoms, rhinopharyngitis is quite similar to the common cold: runny nose, sneezing, sore throat, fever…
And unfortunately, the risks of getting rhinopharyngitis in winter are high! First of all, because there are now more than 100 viruses that can transmit this disease. Then, because it is very contagious and spreads easily, among other things by the contaminated micro-droplets that are released into the air when you cough or sneeze. That’s why it’s important to always put your hands in front of your mouth when you cough and to wash your hands well when you are sick…
5. Bacterial angina
Bacterial angina (also known as strep throat, strep throat or strep throat) is a particularly contagious form of angina that is caused by bacteria belonging to the group A streptococcus (GAS) class. It is transmitted through contact with the saliva and/or respiratory secretions of infected people. That’s why people with bacterial strep throat should wear a mask when they are sick.
In terms of symptoms, bacterial angina is mainly characterized by: fever, chills and sweating, headache and sore throat, white patches on the tonsils, nausea, body aches.
Important: Although strep throat is rarer than viral strep throat, it can lead to complications such as heart disease or rheumatic fever. Hence the importance of testing for strep throat!
The common cold -also known as viral rhinitis- is a very common infectious disease, caused by a rhinovirus type virus, which attacks the nasal cavity and throat. The symptoms of this contagious disease are well known, especially in winter: sore throat, sneezing, blocked nose, runny nose…
And if the cold is such a contagious disease, it is because when the cold viruses are fixed on the mucous membranes of the nose, eyes or mouth, the latter let them pass quite easily!
The common cold is a disease that can be transmitted from one individual to another:
- in case of inhalation of micro-droplets emitted by a sick person when he/she goes to cough or sneeze,
- by hand contact (handshake, etc.) with a contaminated person, or even objects that he or she has touched.
7. Chicken pox
Chickenpox is a viral disease, caused by a virus of the herpes group, the varicella zoster virus (VZV). And even though in the vast majority of cases (90%) it affects children under 10 years of age, chickenpox is a contagious disease that can be caught at any age.
Characterized by skin lesions that evolve in 3 phases (macules, vesicles then crusts) as well as fever, chickenpox is a disease that is transmitted from one individual to another:
- by direct contact with the infected vesicles (by touching them or by being in contact with the liquid they contain),
- or by airborne transmission (via microdroplets emitted when coughing or sneezing).
8. The hand-foot-and-mouth syndrome
As you might expect from the name of this disease, hand-foot-and-mouth syndrome is a disease that mainly affects young children (between 6 months and 4 years old). Extremely contagious (especially in the period from spring to autumn), this disease is most often benign, and involves enterovirus-type viruses.
The foot-hand-mouth syndrome is characterized by symptoms such as: fever, sore throat, abdominal pain, but especially the appearance of small red pimples (vesicles) on the palms of the hands and soles of the feet.
This childhood disease is transmitted by direct and indirect contact through :
- microdroplets (coughs, sneezes),
- nasal secretions,
- handling objects or food touched by a sick person.
Infectious mononucleosis is a contagious disease caused by the Epstein-Barr virus, which mainly affects adolescents and young adults. The most common symptoms are a feeling of intense fatigue, weakness throughout the body, and a sore throat. It is called “kissing disease” because in most cases, the virus is transmitted by direct contact, via saliva!
The Epstein-Barr virus is an extremely common virus (at the age of 40, 90% of individuals are carriers), but it does not always lead to infection. In most cases, it is even harmless. However, in some cases, without knowing why, the first infection with this virus causes mononucleosis.
HIV (Human Immunodeficiency Virus) is an STD (Sexually Transmitted Disease) that is characterized by a progressive destruction of the body’s cells that are supposed to provide immunity. If HIV is not treated, the body is so weakened that a seemingly harmless disease like bronchitis can become very difficult to treat… and therefore fatal.
HIV should not be confused with AIDS (Acquired Immune Deficiency Syndrome) which is a disease that can be caused by HIV (but not always).
HIV is a highly contagious disease that can be transmitted :
- through unprotected sex,
- during contact with contaminated blood (drug addiction, blood transfusions, etc.),
- from mother to child if untreated.