Human Viral Diseases

January 26, 2016 September 24, 2018

Common animal viral diseases include African horse sickness, Foot and mouth disease of cattle, Virus pneumonia of pigs, Rabies etc. Common human viral diseases include Influenza, Measles, Herpes, Dengue, Smallpox, Mumps, Common cold, Hepatitis, AIDS. The recent viral pandemics / epidemics include Ebola Virus Disease, Rift Valley fever, Bolivian hemorrhagic fever, Crimean Congo Hemorrhagic Fever, SARS, and MERS etc.

Flu

Flu is caused by influenza virus, which is a highly mutant virus. Influenza generally spreads through air via cough or sneezes. There are three species of Influenza Virus viz. Influenza-A, Influenza-B, and Influenza-C. Out of them, Influenza A infects birds and mammals. It has very high rate of mutation, and this is the reason that so many different strains of influenza virus are found. In a first, they don’t infect humans, but if they do so, they cause devastating pandemics. The common Influenza outbreaks caused by Influenza-A strains include H1N1 (swine flu) in 2009; and H5N1 (Bird Flu) in 2004. H1N1 is the same strain which causes seasonal outbreaks of flu in humans on a regular basis. Since doctors have found it very hard to predict who will develop complications, it has been dubbed a “Jekyll and Hyde” virus.

Meaning of H and N in Flu
Various strains of Virus differ in certain proteins on the virus surface — hemagglutinin (HA) and neuraminidase (NA) proteins. The scientists give them different names on this bases.

Influenza B and C are less common and are less mutants in comparison to A.

Hepatitis / Jaundice

Hepatitis literally means inflammation of the liver. There are three major types of Hepatitis virus viz. Hepatitis A virus, Hepatitis B virus (HBV) and Hepatitis C Virus (HCV).

A is acute (acute means short term), B is acute as well as chronic (Chronic means long term) while C is almost chronic.
A spreads easily, B spreads relatively less easily and C spreads rarely.
A spreads via food, water etc. and can infect many people at once. For example, a food handler in a restaurant can spread Hepatitis A to many people at once; B spreads by blood or other body floods. C spreads only by blood.
A gets better on its own but can be serious in older people; B is common in India, Asia and Africa. We note here that Amitabh Bachchan has recently revealed that he has lost 75% of is liver to Hepatitis B. C is even more dangerous.
A and B can be prevented by vaccination, but not C. However, there are medicines available to treat C.

AIDS

Human immunodeficiency virus (HIV) also known as human T-lymphotropic virus-III (HTLV-III), lymphadenopathy-associated virus (LAV), and AIDS-associated retrovirus (ARV) is a retrovirus. {Retrovirus means it replicates via reverse transcription} in host cell. It transmits via anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, breastfeeding or other exposure to one of the above bodily fluids.

Due to weakened immune system the person is attacked by infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages.

What is the difference between human immunodeficiency virus (HIV) and AIDS ?

The term AIDS applies to the most advanced stages of HIV infection. The Center for Disease Control (CDC) definition of AIDS includes all HIV-infected people who have fewer than 200 CD4+ T cells per cubic millimetre of blood. (Healthy adults usually haveCD4 + T cell count of 1,000 or more.) The definition also includes 26 clinical conditions (mostly opportunistic infections) that affect people with advanced HIV disease.

Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS may develop various cancers such as Kaposi’s sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Besides the people infected with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss.

Smallpox

Smallpox is one of the three diseases (other two Guinea worm and Polio) that have been eradicated from India. Smallpox was eradicated globally in 1980s. This Virus has been used in biological warfare also. British used smallpox as a biological warfare agent during seven years war in 18th century.

Chickenpox

Chickenpox or varicella is caused by Varicella Zoster Virus (VZV).

Poliomyelitis

Polio virus is an enterovirus which means that the route of entry of this virus is through the gastrointestinal system. It’s an RNA virus. Polio is usually spread via the fecal-oral route (i.e., the virus is transmitted from the stool of an infected person to the mouth of another person from contaminated hands or such objects as eating utensils). Some cases may be spread directly via an oral to oral route.

Measles

Both measles and German measles (rubella) are caused by viruses; and are rashes on the skins. German measles is accompanied by a blotchy red rash. The patient sometimes suffers a slight cold prior to the appearance of the rash. German measles can be dangerous for pregnant women, who have no immunity for the virus. It is called German measles because it was German physicians who first described this disease. Mild upper respiratory affect, high temperature that can last for four days and conjunctivitis are some symptoms of measles.

Rubella or German measles

Rubella (German measles) spreads when infected person coughs or sneezes. It causes a rash, a slight fever, aching joints, headaches, runny nose and red eyes. The virus spread by sneezes or coughs can lead to serious birth defects if contracted by pregnant woman. In 2015, the North and South America region have become the first region of the world to eradicate Rubella. There are no home-grown cases in five years.

Dengue

Dengue virus is transmitted by a bite of female mosquito of any of two species of mosquitoes of the genus Aedes.

The mosquito, which typically bites humans in the daylight hours, can be easily recognized because of its peculiar white spotted body and legs.

Outbreak of the disease typically occurs in summer season when the mosquito population reaches its peak.

Unlike malaria, which is a major health concern in rural areas, dengue is equally prevalent in the urban areas too. In fact, it is predominantly reported in urban and semi-urban areas.

A severe form of the infection is known as dengue hemorrhagic fever (DHF). DHF can be fatal. Because of the severe joint pain, dengue is also known as break-bone fever.

DHF is characterized by a fever that lasts for 2 to 7 days, with general signs and symptoms consistent with dengue fever. In addition to these symptoms, if a patient suspected with dengue experiences decrease in platelets or an increase in blood haematocrit, it becomes more certain that the patient is suffering from the infection. Platelets are cells in blood that help to stop bleeding, while haematocrit indicates thickness of blood. The smallest blood vessels become excessively permeable allowing fluid component to escape from blood vessels to organs of the body. This may lead to failure of circulatory system, which might also cause death.

Chikungunya

This disease is caused by Chikungunya virus transmitted by both Aedes aegypti and Aedes albopictus. The mosquitoes usually transmit the disease by biting infected persons and then biting others. The infected person cannot spread the infection directly to other person.

Symptoms of Chikungunya fever are most often clinically indistinguishable from those observed in dengue fever. However, unlike dengue, haemorrhagic manifestations are rare and shock is not observed in Chikungunya virus infection. It is characterized by fever with severe joint pain (arhralgia) and rash.

Rabies

Rabies or hydrophobia is found among dogs, cats, bats and other wild mammals. The transmission to humans occurs through the saliva of contaminated animals, mainly through bites. The rabies virus is neurotropic and attacks the central nervous system in a fast and lethal fashion. The prevention of the disease is done through the prophylactic vaccination of animals and humans. The treatment is done with an anti-rabies serum containing specific antibodies against the virus.

Yellow Fever

Yellow fever is a viral infection that occurs mainly in Central Africa and in the Amazon region of South America. It is prevented through vaccination and is transmitted by many species of mosquitoes of the Aedes genus, including Aedes aegypti. The infection causes clinical manifestations that range from asymptomatic cases to lethal fulminant cases. Generally, the disease begins a with fever, chills, discomfort, headache and nausea and evolves to jaundice (increase of bilirubin in blood, after which the disease is named), mucosal and internal hemorrhages, hemorrhagic vomiting and kidney failure.

Prevention is done by regular mass vaccination and the vaccination of travelers to endemic areas. The fight against the vector mosquito is also an important prophylactic measure.

Acute Encephalitis Syndrome

Encephalitis refers to acute Inflammation of the brain. There are two main types of encephalitis viz. viral encephalitis and Japanese encephalitis. While Viral encephalitis is caused by water-borne enterovirus; Japanese encephalitis is caused by mosquito Culex tritaeniorhynchus and Culex vishnui. Every monsoon sees an outbreak of acute encephalitis syndrome, or AES, diseases. Japanese encephalitis and viral encephalitis diseases; and both of these make the Acute encephalitis syndrome, or AES. This disease is called a poor man’s disease and affects largely to paddy farmers.