1. Cold
The common cold (also known as nasopharyngitis, rhinopharyngitis, acute coryza, head cold, or simply a cold) is a viral infectious disease of the upper respiratory tract which primarily affects the nose.
Signs and symptoms include coughing, sore throat, runny nose, sneezing, and fever which usually resolve in seven to ten days, with some symptoms lasting up to three weeks. Well over 200 virus strains are implicated in the cause of the common cold; the rhinoviruses are the most common.
Key points
* Upper respiratory tract infections are loosely divided by the areas they affect, with the common cold primarily affecting the nose, the throat (pharyngitis), and the sinuses (sinusitis), occasionally involving either or both eyes via conjunctivitis.
* Symptoms are mostly due to the body's immune response to the infection rather than to tissue destruction by the viruses themselves.
* The primary method of prevention is by hand washing with some evidence to support the effectiveness of wearing face masks.
* The common cold may occasionally lead to pneumonia, either viral pneumonia or secondary bacterial pneumonia.
2. Chicken pox
Chicken pox, also known as varicella, is a highly contagious disease caused by the initial infection with varicella zoster virus (VZV). The disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab over. It usually starts on the face, chest, and back and then spreads to the rest of the body.
Other symptoms may include fever, feeling tired, and headaches. Symptoms are usually last five to ten days. Complications may occasionally include pneumonia, inflammation of the brain, or bacterial infections of the skin among others. The disease is often more severe in adults than children. Symptoms begin ten to twenty one days after exposure to the virus.
Key points
* Chicken pox is an airborne disease which spreads easily through the coughs and sneezes of an infected person.
* It may be spread from one to two days before the rash appears until all lesions have crusted over.
* It may also spread through contact with the blisters.
3. Small pox
Smallpox was an infectious disease caused by either of two virus variants, Variola major and Variola minor. The last naturally occurring case of small pox (Variola minor) was diagnosed on 26 October 1977. Infection with smallpox is focused in small blood vessels of the skin and in the mouth and throat before disseminating. In the skin it results in a characteristic maculopapular rash and, later, raised fluid-filled blisters.
4. Measles
Measles, also known as morbilli, rubeola, or red measles, is a highly contagious infection caused by the measles virus. Initial signs and symptoms typically include fever, often greater than 40 °C (104.0 °F), cough, runny nose, and red eyes. Two or three days after the start of symptoms, small white spots may form inside the mouth, known as Koplik's spots.
Symptoms usually develop 10 – 12 days after exposure to an infected person and last
7 – 10 days. Complications occur in about 30% and may include diarrhea, blindness, inflammation of the brain, and pneumonia among others. Rubella (German measles) and roseola are different diseases.
Key points
* Measles is an airborne disease which spreads easily through the coughs and sneezes of those infected.
* It may also be spread through contact with saliva or nasal secretions.
5. Mumps
Mumps, also known as epidemic parotitis, is a viral disease caused by the mumps virus. Initial signs and symptoms often include fever, muscle pain, headache, and feeling tired. This is then usually followed by painful swelling of one or both parotid glands. Symptoms typically occur 16 to 18 days after exposure and resolve after 7 to 10 days. Symptoms in adults are often more severe than in children. About a third of people have mild or no symptoms. Complications may include infections of the coverings of the brain (15%), pancreatitis (4%), permanent deafness, and painful testicular swelling which uncommonly results in infertility. Women may develop ovarian swelling but this does not increase the risk of infertility.
Key points
* It is highly contagious and spreads rapidly among people living in close quarters.
* The virus is transmitted by respiratory droplets or direct contact with an infected person.
* Only humans get and spread the disease.
* People are infectious to each other from a few days before the start of symptoms to four days after.
6. Chikungunya
Chikungunya is an infection caused by the chikungunya virus. It features the sudden onset of fever usually lasting two to seven days, and joint pains typically lasting weeks or months but sometimes years. The mortality rate is a little less than 1 in 1000, with the elderly most likely to die.
The virus is passed to humans by two species of mosquito of the genus Aedes:
A. Albopictus
B. Aegypti.
Animal reservoirs of the virus include monkeys, birds, cattle, and rodents. This is in contrast to dengue, for which only primates are hosts.
Key points
* The best means of prevention is overall mosquito control and the avoidance of bites by mosquitoes in countries where the disease is common.
* No specific treatment is known, but medications can be used to reduce symptoms.
* Rest and fluids may also be useful.
7. Dengue fever
Dengue fever, also known as breakbone fever, is a mosquito-borne tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles.
In a small proportion of cases, the disease develops into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.
Dengue is transmitted by several species of mosquito within the genus Aedes, principally A. aegypti. The virus has five different types. Infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications. As there is no commercially available vaccine, prevention is sought by reducing the habitat and the number of mosquitoes and limiting exposure to bites.
8. Rabies
Rabies is a viral disease that causes acute inflammation of the brain in humans and other warm-blooded animals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms:
* Violent movements, uncontrolled excitement
* Fear of water
* An inability to move parts of the body
* Confusion
* Loss of consciousness
Rabies is caused by lyssaviruses including: rabies virus and Australian bat lyssavirus. Rabies is spread when an infected animal scratches or bites another animal or human. Saliva from an infected animal can also transmit rabies if the saliva comes into contact with the mouth, nose, or eyes. Overall dogs are the most common animal involved. More than 99% of rabies cases in countries where dogs commonly have the disease are caused by dog bites.
9. Severe Acute Respiratory Syndrome (S.A.R.S)
Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the SARS coronavirus. Between November 2002 and July 2003, an outbreak of SARS in southern China caused an eventual 8,096 cases and 774 deaths reported in multiple countries with the majority of cases in Hong Kong (9.6% fatality rate) according to the World Health Organization (WHO). Within weeks, SARS spread from Hong Kong to infect individuals in 37 countries in early 2003. It then was eradicated by January the following year.
Initial symptoms are flu-like and may include fever, myalgia, lethargy symptoms, cough, sore throat, and other nonspecific symptoms. The only symptom common to all patients appears to be a fever above 38°C (100°F). Shortness of breath may occur later. The patient has symptoms as with a cold in the first stage, but later on they resemble influenza. SARS may occasionally lead to pneumonia, either direct viral pneumonia or secondary bacterial pneumonia.
10. Hepatitis
Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. Hepatitis may occur with limited or no symptoms, but often leads to jaundice, poor appetite, and malaise. Hepatitis is acute when it lasts less than six months and chronic when it persists longer.
Acute hepatitis can be self-limiting, can progress to chronic hepatitis, or, rarely, can cause acute liver failure. Chronic hepatitis may have no symptoms, or may progress over time to fibrosis and cirrhosis. Cirrhosis of the liver increases the risk of developing hepatocellular carcinoma (a form of liver cancer).
11. Japanese Encephalitis
Japanese encephalitis is a disease caused by the mosquito-borne Japanese encephalitis virus (JEV). The Japanese encephalitis virus (JEV) itself is a virus from the family Flaviviridae, part of the Japanese encephalitis serocomplex of 9 genetically and antigenically related viruses, some which are particularly severe in horses, and four known to infect humans including West Nile virus.
Domestic pigs and wild birds (especially herons) are reservoirs of the virus; transmission to humans may cause severe symptoms. Amongst the most important vectors of this disease are the mosquitoes Culex tritaeniorhynchus and Culex vishnui. This disease is most prevalent in Southeast Asia and East Asia.
12. Polio
Poliomyelitis, often called polio or infantile paralysis, is an infectious disease caused by the poliovirus. Poliovirus is usually spread from person to person through infected feces entering the mouth. It may also be spread by food or water containing human feces and less commonly from infected saliva. Those who are infected may spread the disease even if no symptoms are present for up to six weeks. The disease may be diagnosed by finding the virus in the feces or detecting antibodies against it in the blood.
13. Cancer
Cancer also known as a malignant tumor or malignant neoplasm, is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Not all tumors are cancerous; benign tumors do not spread to other parts of the body. Possible signs and symptoms include: a new lump, abnormal bleeding, a prolonged cough, unexplained weight loss, and a change in bowel movements among others. While these symptoms may indicate cancer, they may also occur due to other issues. There are over 100 different known cancers that affect humans.
Tobacco use is the cause of about 22% of cancer deaths. Another 10% is due to obesity, a poor diet, lack of physical activity, and consumption of ethanol (alcohol). Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. In the developing world nearly 20% of cancers are due to infections such as hepatitis B, hepatitis C, and human papillomavirus.
14. AIDS
Human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV). Following initial infection, a person may experience a brief period of influenza-like illness. This is typically followed by a prolonged period without symptoms. As the infection progresses, it interferes more and more with the immune system, making the person much more susceptible to common infections like tuberculosis, as well as opportunistic infections and tumors that do not usually affect people who have working immune systems. The late symptoms of the infection are referred to as AIDS. This stage is often complicated by an infection of the lung known as pneumocystis pneumonia, severe weight loss, a type of cancer known as Kaposi's sarcoma, or other AIDS-defining conditions.
15. Influenza
Influenza, commonly known as "the flu", is an infectious disease caused by the influenza virus. Symptoms can be mild to severe. The most common symptoms include: a high fever, runny nose, sore throat, muscle pains, headache, coughing, and feeling tired. These symptoms typically begin two days after exposure to the virus and most last less than a week. The cough, however, may last for more than two weeks. In children there may be nausea and vomiting but these are not common in adults. Nausea and vomiting occur more commonly in the unrelated infection gastroenteritis, which is sometimes inaccurately referred to as "stomach flu" or "24-hour flu". Complications of influenza may include viral pneumonia, secondary bacterial pneumonia, sinus infections, and worsening of previous health problems such as asthma or heart failure.
Three types of influenza affect people. Usually, the virus is spread through the air from coughs or sneezes. This is believed to occur mostly over relatively short distances. It can also be spread by touching surfaces contaminated by the virus and then touching the mouth or eyes. A person may be infectious to others both before and during the time they are sick. The infection may be confirmed by testing the throat, sputum, or nose for the virus. A number of rapid tests are available; however, people may still have the infection if the results are negative. A type of polymerase chain reaction that detects the virus's RNA is more accurate.
