Understanding Diseases: Acute, Chronic & Communicable

• Diseases can be classified by healing time as either chronic or acute.
• Chronic diseases are long in duration and involve very slow changes.
• Asthma and Type 2 diabetes are examples of chronic diseases.
• Acute diseases come on quickly but last for a short time, usually less than three months.
• Acute diseases tend to have severe symptoms, such as seasonal flu and Measles.
• Diseases can be classified as communicable and non-communicable.
• Infectious and genetic diseases are covered mainly in the chapter.
• Non-communicable diseases like cancer will be covered later.
• Health used to be defined exclusively as the absence of disease or physical fitness.
• Health is now defined as a state of complete physical, mental and social well-being.
• A disease is a disorder with a specific cause and recognizable signs and symptoms, or any bodily abnormality or failure to function properly.
• Diseases are not a result of physical injury necessarily.
• Each disease is associated with a set of signs and symptoms that differ from each other.
• Signs are changes in body function that a physician can detect and measure, like elevated blood pressure.
• Symptoms are what a patient reports experiencing.

Infectious Diseases

• Infectious diseases are caused when microorganisms known as pathogens enter and spread within the body.
• Viruses, bacteria, fungi, protozoa, and helminths are examples of pathogens.
• Infectious diseases have ravaged peoples and populations worldwide throughout history.
• Infectious diseases are considered primary disease-related causes of death, like cholera, smallpox, plague, and Spanish influenza.
• The causes of these diseases were not understood until the 1850s.

Pathogens - Virus

• Viruses range in size from 20 to 300 nm.
• Viruses are not cells and do not carry any metabolic organelles found in prokaryotes or eukaryotes.
• Viruses cannot reproduce by themselves.
• A virus needs to enter the target cell in the host's body; once inside it controls the cell's machinery to reproduce.
• Viruses are an example of a disease cause, like Smallpox, hepatitis, SARS, and AIDS.

Pathogens - Bacteria

• Bacteria range in size from 0.4 mm to 2.0 mm.
• Most bacteria can reproduce and grow independently.
• Bacteria can also reproduce without invading and seizing the metabolic functions of host cells.
• Cholera, tuberculosis, and pneumonia are examples of bacteria related diseases.

Categories of Diseases

• Communicable/Infectious diseases are caused by germs; can be transmitted directly or indirectly.
• Covid-19, influenza and Cholera are examples of communicable diseases.
• Non-communicable diseases are not transmissible and tend to be of long duration.
• Non-communicable diseases result from a mix of genetic, physiological, environmental and behavioral factors.
• Cardiovascular disease, stroke, certain cancers, and asthma are examples of non-communicable diseases.
• Genetic/inherited diseases arise from defects in genes or chromosomes.
• Down syndrome, Thalassemia and sickle cell are examples of genetic or inherited diseases.
• Metabolic diseases are caused by abnormal chemical reactions, Diabetes and hyper-tension are examples.
• Degenerative diseases cause the function of tissues, organs or body structure to decline over time.
• Parkinson's disease and Alzheimer's disease are examples of degenerative diseases.

Transmission of Infectious Diseases

• An infectious disease can spread in different ways and in varying patterns.
• The classification for infectious diseases is according to occurrence and prevalence in the community.
• Endemic infectious diseases spread only within a given region at a relatively low level of infection.
• Malaria is endemic in tropical and subtropical areas.
• Epidemic infectious diseases involve a sudden outbreak that spreads rapidly, affecting a large proportion of people.
• Cholera is an example of an epidemic disease.
• Pandemic diseases involve a disease outbreak over a wide geographic area (continent or worldwide).
• Covid-19 is an example of a pandemic disease.
• Modes of transmission fall into two broad categories: direct and indirect transmission methods.

Transmission - Direct

• Direct transmission occurs through human physical contact, like shaking hands, saliva, and sexual contact.

Transmission - Indirect

• Indirect transmission happens through touching an object contaminated with pathogens from coughs or sneezes.
• Some pathogens travel through the air for a long distance.
• Diseases are occasionally transmitted through vectors such as mosquitoes, ticks, lice, flies, and fleas.
• Diseases can be transmitted indirectly through contaminated food and water.
• Blood transfusions can transmit disease, for example hepatitis B.
• Respiratory droplets spread some diseases.
• Diseases can be transmitted through reptiles and birds, but is not as common.
• Animals can directly trasmit infections to humans.

Viral Diseases - Examples

• Viruses associated with respiratory infections can invade and replicate in the respiratory tract's epithelial cells.
• Respiratory infections can cause respiratory and systemic symptoms.
• Coronavirus belongs to the Coronaviridae family and affects the respiratory system.
• Coronaviruses are named for the crown-like spikes on their surface.
• Seven human coronaviruses (HCoVs) have been identified since the mid-1960s.
• Coronaviruses can infect vertebrates, causing diseases in humans, birds, bats, snakes, mice, and other wild animals.
• SARS is considered one of the most dangerous types and spread in 2003 in China
• MERS is an example of a respiratory disease that broke out in 2012.
• Novel coronavirus (Covid-19) first spread in China, specifically Wuhan, in 2019.

SARS

• SARS is a respiratory viral disease caused by SARS-CoV and belongs to the Corona family.
• SARS was the first acute and rapidly spreading new disease of the 21st century.
• The SARS virus infected 8,422 persons and caused 919 deaths.
• There are no antiviral treatments or vaccines for SARS.
• All treatments are given to patients only as supportive, which also depend on the patient's symptoms.

MERS-CoV

• MERS-CoV is a zoonotic virus carried by dromedary camels.
• MERS-CoV is transmitted to humans through direct contact with camels or from food/waste products.
• MERS-CoV is not easily transmitted from one person to another without direct contact.
• In hospital, diagnosis delays lead to secondary cases among health care workers.
• The incubation period for MERS-CoV is between 2 and 14 days.
• Dipeptidyl peptidase 4 (DPP4, also known as CD26) is a multifunctional cell surface protein.
• DDP4 receptor is widely expressed on epithelial cells in the lungs, kidneys, small intestine, liver, and prostate.
• Having receptors in various organs allows the MERS-CoV virus to infect several human cell lines.
• Treatment for MERS-Cov infection include no vaccines or anti-virals that can protect or treat this infection.
• Treatment for MERS-Cov aims to reduce complications due to the virus via supportive care.
• Diagnosis for MERS-CoV is determined via a Real-time Polymerase Chain Reaction (RT-PCR).
• Clinical manifestations range from asymptomatic to severe disease with mild symptomology.
• Mild symptoms can be fever with tremor, dry cough, muscle pain (myalgia), and gastrointestinal symptoms like diarrhea, vomiting, nausea, and sometimes stomach ache.
• Symptoms of severe cases include respiratory failure, acute respiratory distress syndrome, organ failure, and septic shock.
• The median period to the intensive care unit is two days after hospitalization.

COVID-19

• COVID-19 virus transmits through close contact from person to person, by touch, and aerosol
• The direct contact is transmission of respiratory droplets from one person to another.
• When an infected person coughs or sneezes, the droplets can travel 3 feet and deposit on the mucous membranes of the mouth, nose, or eyes.
• The indirect contact is transmitted by touching contaminated surfaces.
• The incubation period of COVID-19 is typically 5-6 days, though it can be up to 14 days.
• The virus reaches the lung through the mucous membranes and binds to ACE2, a receptor on the target cells' surface in the lungs.
• ACE2, an entry point, also appears in different organs affecting the heart, renal system, and gastrointestinal tract.
• The most common symptoms for mild cases include dry cough, fever, and tiredness.
• Less common symptoms include aches, pains, sore throat, diarrhea, conjunctivitis, headache, loss of taste or smell, rash, and discoloration.
• Patients suspected of having the virus are diagnosed by collecting nasopharyngeal or oropharyngeal swabs.
• Swabs are analyzed by real-time Polymerase Chain Reaction (PCR), the procedure tests and provides an effective, direct method.
• There are no specifc antiviral treatment recommended to destroying the COVID-19 virus itself.
• Initial treatment isolates to prevent spread.
• Treatment is applied according to severity, including oxygen, ventilation, and, sometimes, daily monitoring or assessment.
• There are multiple vaccines approved bby the WHO.
• The Pfizer/BioNTech listed (approved) in December 2020
• Sinopharm vaccine listed in May 2021
• The Moderna COVID-19 vaccine (mRNA 1273) listed in April 2021
• The Janssen/Ad26.COV 2.S developed by Johnson & Johnson, listed in March 2021

Bacterial Diseases - Tuberculosis

• Tuberculosis (TB) is a communicable disease that affects the lungs, previously called the white plague in Europe.
• TB can affect the lungs as pulmonary tuberculosis or sites other than the lungs as extrapulmonary TB.
• Humankind has been plagued with TB since antiquity.
• TB is one of the most prevalent infectious diseases in the world and one of the first ten causes of death.
• The statistics from the World Health Organization (WHO) in 2019: nearly 10 million people became infected, 1.4 million people died.
• Approximately half of all people with TB can be found in eight countries: Bangladesh, China, India, Indonesia, Nigeria, Pakistan, Philippines, and South Africa.
• TB is mainly in adults, plus its is two times higher in adult men when related to an active infection.
• The causative agent is the bacterium bacilli called Mycobacterium tuberculosis.
• The pathogen remained unknown until Dr. Robert Koch discovered it in the early 19th century.
• TB infections are quite frequent in infants, there are less children between ages 2-10 years.
• People with HIV infection and type 2 diabetes mellitus have a higher risk of developing the disease.
• Other risk factors are alcohol consumption, low body mass index, smoking, air pollution, and injection drug users.
• The most prevalent societies where the disease are the poor societies, immigrants, the homeless, and prisoners.

Way of TB transmission

• Tuberculosis is an airborne nature disease that is transmitted.
• The pathogen spreads from person to person by inhaling particles called droplets nuclei.
• Droplets nuclei are produced when the infected person coughs, sneezes, or from dry sputum.
• The particles containing tubercle bacilli are small, from 1-10 bacilli (1–5 µm), and remain suspended in the air for several hours.
• Tuberculosis can be a latent or active infection.
• Active TB may develop quickly and is transmissible.
• Latent Tuberculosis infection (LTBI) remains inactive for several years in the body, around 1-2 years.
• Signs and symptoms of TB include coughing for a prolonged time, including blood, chest pain, weakness or fatigue, weight loss, fever, and night sweats.
• Sputum samples is taken and cultivated to diagnose the germs.
• Radiography X-rays are used with clinical suspicion, but when spuntum is negative.
• The Tuberculin Skin Test (TST) is used to detect infection with Mycobacterium tuberculosis.

Viral Disease - Rotavirus

• Classified by the family of Reoviridaea, rotavirus is one of the leading causes of viral enteritis.
• There are seven groups of rotavirus (A through G), but human ailments primarily stem from group.
• Rotavirus is most prevalent during the winter season.
• The virus is transmitted via the fecal-oral route.
• Common transmission is contact with contaminated water, food, or objects such as a toy or baby bottle.
• Adults become infected through contact with children infected with the virus.
• Adults are often asymptomatic due to breast milk and maternal antibodies.
• Group B rotavirus is the most common among adults.
• Cases have been detected in China and Southeast Asia.
• Rotaviruses infect the villi in the small intestine and proliferate in the cytoplasm of intestinal cells, damaging the transport mechanism.
• The incubation period is shown to be from 1-3 days
• Clinical manifestation ranges from asymptomatic to acute gastroenteritis, leading to life-threatening dehydration.
• Severe diarrhea occurs in infants and children from loss of fluids/minerals, and death.
• The signs and symptoms of the disease include watery diarrhea, fever, abdominal pain, and vomiting.
• Diagnoses include Nucleic acid detection using enzyme immunoassays (EIAs) or PCR tests used to detect the virus.
• Treat with supportive care involving fluid and electrolyte replacement to treat diarrhea.
• Oral rehydration therapy or intravenous fluid if the patient cannot tolerate oral treatment is possible.
• Sanitation and sterilization of water helps control the virus
• Vaccine to help prevent this infection comes from live attenuated samples.

Cholera

• Cholera is an acute diarrheal disease that affects the small intestine, caused by a bacterium called Vibrio cholera.
• A cholera outbreak can spread due to crowding, war, famine, and due to poor sanitation.
• Original reservoir was originally in the Ganges River delta, but now it has spread worldwide.
• Cholera has spread worldwide through several outbreaks over the centuries as well from earthquakes.
• The estimated number of annually infected people with this disease globally ranges from 1.3 - 4 million.
• The annual deaths due to Cholera ranges between 21,000- 143,000 people.
• Cholera can be found outside the body in cold, alkaline water, mostly contaminated with organic matter or feces.
• Cholera is contracted through the ingestion of shellfish, crustaceans, or contaminated food.
• Most people with Vibrio cholera show no symptoms after infection, although the bacteria are present in their stools from 1-10 days.
• Then they return the infection to the environment infecting other people.
• Cholera affects both children and adults. V.cholerae penetrates the intestinal mucosa, multiplies, and releases an intestinal toxin.
• The incubation period for the pathogen is 12 hours to 5 days
• Typical signs and symptoms of cholera infection are severe vomiting, nausea, diarrhea, abdominal pain, and rice water stool.
• Stool contains mucus plugs with a fishy odor, severe dehydration, and hypotension.
• Fast antigen tests such as dipstick feces assays or microbiological culturing can diagnosis Cholera
• replace lost bodily fluids to help treat this
• prepare your own oral remedy to add one teaspoon of table salt to 1 L of water.
• Antibiotics can counter related bateria

Immunity

• The immune system enables our bodies to resist external factors that enable germs, bacteria, and potential pathogens to attack the body.
• Innate and adaptive, there are two types of Immunity and their defense lines.
• Innate immunity is a non-specific type of defense, present from birth, working against any invading agents.
• Physical barriers prevent the entry of germs (i.e. the skin, mucous membranes, digestive system)
• Chemical barriers include gastric juices, saliva, and tears aid in preventing germs.
• Cellular barriers include white blood cells swallow infections microorganisms.
• Inflammation includes symptoms like redness, swelling, and temperatures increase.
• Fever eliminate the invading germs produce deactivate toxic substance.
• Molecular barriers is creating substance to destroy invasive microbes.
• Adaptive immunity is a result of exposure to pathogens.
• The acquired immunity will either stimulating our immune system or injecting a vaccine with bacteria antigen.
• the body acquires it as a result of natural exposure to molecules called antigens during illness,
• T lymphocytes and B lymphocytes activate to fight germs.
• In artificial immunity injecting the body with the antigen stimulates antigens in our system, which can last for a long or short period of time depending on various factor.
• The source is that antibodies must work with our systems

Vaccination

• Vaccines are substances containing the antigen.
• Attenuated vaccine involves injecting a weak form of the germs.
• Only one or two doses of most live vaccines can provide life-long protection against germs and the disease they cause.
• The vaccines are rotavirus, smallpox, measles, mumps can support immunity
• Antibodies are naturally acquired for natural exposure to pathogens, plus, it eliminates germs.
• Passive antibodies are passed through reaction that isn't the body.

Thalassemia Definition

• The hemoglobin protein in red blood cells transport and carry oxygen.
• Each hemoglobin molecule has two subunits/chains: alpha and beta
• Four copies of the alpha-globin genes control the production of alpha chains
• Two copies of the beta-globin genes producing beta chains.
• Thalassemia is a blood-related disorder is identified by its lack of reduced hemoglobin.
• Alpha and Beta chain affect chromosomes 16 and 11.

Types Of Thalassemia

• Alpha thalassemia are genes one or more destroyed or in ways different for alpha Globin
• Alpha and beta is not defect but normal blood
• Beta globin has one or two destroyed or altered
• Beta is a defect and only symptoms
• No Beta produced is the major disorder