Microbiology is one of the Biology Topics that involves the study of microorganisms, including bacteria, viruses, and fungi.
Human Diseases Caused by Viruses
Influenza (flu) – Symptoms and Causes
Influenza is commonly called flu. It is caused by an influenza virus (Myxovirus influenza). There exist three types of influenza viruses – A, B, and C. A and B types of influenza viruses are important because they are responsible for causing disease epidemics throughout the world. The inhaled virus attacks the epithelial cells in the mucous membrane of the nose, throat, and upper respiratory tract.
Influenza is spread mainly from person-to-person contact and by droplet infection via sneezing, coughing, or talking. The common symptoms of influenza disease are sudden onset of chills, discharge from the nose, sneezing, fever, headache, muscular pains, coughing, inflammation of respiratory mucosa, and general weakness. Fever lasts for three days in adults.
Prevention of Influenza:
We should try to keep away from flu patients.
Control of Influenza:
There is no effective control for influenza. However, vaccines are used for the control of infection and antiviral drugs are used for cure. Amantadine and Rimantidine are recommended for the treatment of influenza. Rest speeds up the recovery.
Types of Hepatitis
Jaundice or hepatitis is a disease of the liver. Since the liver is a very important organ in the body, so its inflammation due to jaundice affects digestion adversely. Jaundice is caused by viral infection. The types of hepatitis are Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, Hepatitis E, and Hepatitis G. Except for type B which is a DNA virus, all the others are RNA viruses. Hepatitis is spread mostly by food and water contaminated with the hepatitis virus.
Hepatitis A (or infectious hepatitis by an RNA-containing virus) is an acute infectious disease of the liver that affects mainly children and young adults. Transmission of hepatitis A virus (HAV) takes place by the fecal-oral route, i.e., infection of HAV takes place by ingestion of contaminated water, food, or milk.
Symptoms of Hepatitis A:
- High temperature, headache, fatigue, general weakness, and joint pains.
- Loss of appetite (called anorexia) with a feeling of nausea and vomiting.
- The appearance of irritating rashes on the body.
- Dark yellow urine.
- Light-colored stool after 3 to 10 days of infection.
Prevention of Hepatitis A:
For avoiding infection of hepatitis A preventive measures should be taken.
- Use chlorinated, boiled, and ozonized water.
- Proper cleaning of hands after handling the bed and vessels of the patient.
- Hepatitis-A vaccine should be taken to prevent the disease.
Control of Hepatitis A:
- The application of interferon injection on the advice of the doctor will control the disease.
- For an early cure, it is essential that a patient with jaundice takes adequate rest.
- Jaundice patients should take a high-calorie diet such as juice of sugarcane, and radish with gur (jaggery).
- Consumption of protein and fat should be limited.
Hepatitis B is also known as serum hepatitis or transfusion hepatitis (by a double-stranded DNA virus). This is the most dangerous and widespread type of viral hepatitis. (Hepatitis B is regarded as more dangerous than AIDS). It occurs due to infection of the Hepatitis B virus (HBV). HBV is a blood-borne DNA virus. The infection of HBV is transmitted by infected blood, inoculation (Inoculation means the introduction of a vaccine into a living being to give immunity), from mothers to their babies, and by sexual route (through the semen, saliva, etc.).
The main symptoms of Hepatitis B include progressive liver disease, chronic active hepatitis, and hepatocellular carcinoma (i.e., a malignant cancer of liver cells). Infection of HBV can be prevented by avoiding risky practices such as free or promiscuous sex (Promiscuous means sexual contact which is not restricted to one sexual partner), injectable drug abuse, and direct or indirect contact with blood, semen, and other body fluids of patients of Hepatitis B. Hepatitis B vaccine should be taken to prevent disease.
Hydrophobia of Human Rabies
The bite of a rabid dog (mad dog) and some other rabid mammals such as monkeys, cats, or rabbits may cause rabies, which is a fatal viral disease caused by a rabies virus or lyssavirus which is present in the saliva of the infected animals. The viruses are injected into human blood by the bite of the rabid animal. Disease symptoms are not visible after infection even up to 1 to 3 months. The long period of incubation makes it possible for a rabies vaccination, after a bite, to develop immunity and prevent the appearance of disease.
Symptoms of Rabies:
Rabies is characterized by severe headache, high fever, and painful contraction of muscles of the throat and chest (due to which there is difficulty in swallowing). The patient feels restless, does excessive salivation, has a choking feeling, and finds difficulty in the intake of even liquid food. Since the patient develops a fear of water, the disease is also called hydrophobia.
Prevention of Rabies:
- Cleaning the wound with carbolic soap and clear water immediately after the dog bite is an important preventive measure. Any antiseptic medicine (e.g., Savalon, Dettol) should be applied to the wound caused by a dog bite. A doctor should be immediately consulted for the application of an anti-rabies vaccine to the patient.
- Compulsory immunization of stray dogs and cats should be done. Pet dogs should be vaccinated with the anti-rabies vaccine.
- A rabid animal shows excessive salivation and tries to seek isolation after a bite. Such mad animals should be killed.
Control of Rabies:
Rabies can be treated with Pasteur’s treatment (discovered by Louis Pasteur), in which a course of 14 vaccines was given. Currently, 5 anti-rabies vaccines are prescribed at an interval of 0-3-7-14-30 days after a dog bite.
HIV and AIDS: Symptoms, Causes, Treatments
AIDS stands for Acquired Immuno Deficiency Syndrome. It is a fatal disease. The disease of AIDS is caused by a retrovirus (an RNA virus) known as Human Immunodeficiency Virus (HIV). AIDS virus attacks the white blood cells (WBCs) or lymphocytes (T4 helper cells) of human beings and weakens the human body’s immunity or self- defence mechanism.
Since the AIDS virus reduces the natural immunity of the human body, therefore, patients suffering from AIDS become prone to many other infections or diseases. In fact, patients suffering from AIDS die from other infections (called secondary infections). Death occurs because the patient’s body cannot resist the attack of pathogens of secondary infections since the patient’s natural defence mechanism gets destroyed by an AIDS virus.
Transmission of AIDS:
AIDS disease spreads among human beings in the following ways:
- The AIDS disease usually spreads through unprotected (i.e., without the use of a condom; a condom is a membranous penile sheath of rubber having an anti-venereal or contraceptive function) sexual contact with an infected person carrying the AIDS virus. Thus, AIDS is a sexually transmitted viral disease.
- The AIDS disease also spreads through the transfusion of blood contaminated with an AIDS virus.
- The AIDS disease also spreads through the use of infected needles for injections (i.e., sharing of infected injection needles which have not been sterilized).
- An AIDS-infected mother can transmit the virus to her child during pregnancy or during birth (i.e., by mother’s blood). This is called vertical transmission.
AIDS was first detected in the USA in 1981 and in India, the first confirmed evidence of AIDS infection came in April 1986 from Tamil Nadu. The AIDS disease has spread in epidemic form in Africa and Western countries. This is because of undesirable sexual practices, polygamy, and polyandry. Recently alarmingly increasing cases of AIDS have been reported from different parts of India.
Symptoms of AIDS:
ome important symptoms of AIDS are the following: swollen lymph nodes; regular fever; sweating at night and weight loss. AIDS virus causes severe damage to the brain and may lead to loss of memory, ability to speak, and of clear thinking.
Prevention and Control of AIDS:
So far no medicine or vaccine has been developed to cure AIDS, so, once a person gets AIDS, he is sure to die in a short span of time.
The following steps may help in controlling infection of this dreaded disease:
- People should be educated about AIDS transmission.
- Disposable syringes and needles should be used for injection.
- Sexual contact with unknown people should be avoided.
- High-risk groups should refrain from donating blood.
- Sterilized needles may be provided to drug addicts.
- Before receiving blood for transfusion, one should ensure that it has been screened for HIV.
- The common razor at the barber’s shop should not be used.
Polio – Symptoms and Causes
Poliomyelitis or polio is a disease of the nervous system caused by one of the smallest known viruses, called the polio virus. The virus enters the body through food and water and reaches the intestine and from there, it enters the CNS or central nervous system (brain and spinal cord) via the bloodstream and lymphatic systems. In CNS, the virus destroys the motor nerve cells of the spinal cord that are responsible for the muscular control. Therefore, the muscles of a polio-infected person become incapable of carrying out normal functions. Polio is a kind of paralysis and mostly affects the legs. Children between the age of 6 months and 3 years are most prone to polio infection.
Polio is transmitted among children by the faeco-oral route and through direct contact, dirty hands, contaminated food or milk, and flies. Faeco-oral route of infection of disease includes the transmission of infection via food/ water that is contaminated by the stool of a patient.
Symptoms of Polio:
The early symptoms of the polio disease are sore throat and headache. If the infection persists, the patient suffers from fever, vomiting, muscular pain, stiffness in the neck, tingling sensation in limbs, and ultimately paralysis. Sooner or later polio results in atrophy of skeletal muscles and results in deformity of the affected limb.
Prevention of Polio:
Complete rest and physiotherapy is helpful at the beginning of a poliovirus attack. Exercising of legs is done to reduce the paralytic effect. Maintenance of hygiene by proper sanitary disposal of waste is an essential step for the prevention of polio. Nowadays Oral Polio Vaccine (OPV) is given orally to children as per National Immunisation Schedule in our country. OPV is a live attenuated (diluted or weakened) viral strain taken by mouth which colonizes the gut and induces immunity.
Pulse Polio Immunisation Programme (PPIP): The pulse polio immunization program forms the largest single-day public health project. Pulse means a dose of a substance (here polio vaccine) especially when applied over a short period of time. It was conducted for the first time in December 1995, in an attempt to eradicate polio from our country. This programme uses the oral polio vaccine or OPV.
As per the National Immunisation Schedule (NIS), a dose of 3 drops (0.5 ml) is given orally to the child, i.e., one dose each at 1.5, 2.5, and 3.5 month’s age. Finally, a booster dose is given at the age of 1.5 years. The vaccine consists of milder forms of polio viral particles. After oral administration, virus particles in the vaccine begin to live in the intestine of the human body and multiply. It leads to the production of protective molecules (antibodies) in the intestine and the blood.
The prefixed days, on which pulse polio immunization is to be carried out throughout, the country, are called National Immunisation Days (NIDS). In 1996-1997 the target age group was increased to all children under 5 years of age. From 1999-2000, this programme covers mass immunisation of target groups on 4 occasions (4 NIDS or National Immunisation Days).
The pulse polio immunization campaign seems to be a successful programme. Since the incidence of poliomyelitis in India has decreased dramatically, India recorded 4,791 cases of polio in 1994; 2,489 in 1997; 1600 in 2002; 225 in 2003, and 135 in 2004 (Renu Verma 2011).
Aims of the Pulse Polio Immunisation Programme (PPIP)
- To immunise those children who are not earlier immunised or are partially immunised.
- To replace the disease-causing wild virus with a harmless vaccine virus in the environment.
Message to the Public Regarding PPIP
- Routing polio vaccination in children at birth, 6 weeks, and 10 weeks of age is essential.
- Additional doses of vaccine on National Immunisation Days to boost the immunity of children of the target age group.
- No harm to even sick children who are given polio drops.
- Polio drops (vaccine) are completely safe.
- The general public should cooperate with the Government to achieve the ‘Goal of Polio Eradication, from India’.