We can start our article with a simple answer to the question “What Is Infectious Diseases?”, Infectious diseases are caused by pathogenic bacteria and viruses.
Bacteria, influenza, fungi, and worms/helminths are common examples.
What Is Infectious Diseases signs may not appear under normal conditions because the host’s immune system is completely functioning.
Infectious Diseases develop when the immune system of the host is weakened or when the infectious agent overwhelms the immune system.
Bacteria, influenza, protozoa, helminths, rickettsia, and fungi are the most common causes of infection. Slow-progressing brain diseases like Creutzfeldt-Jakob Disease are caused by prions.
It appeared that infectious diseases, especially bacterial infections, would no longer be a major public health concern after the discovery of penicillin.
However, with the rise of drug-resistant bacteria, lethal infectious diseases like AIDS, and extreme acute respiratory syndrome (SARS) caused by Coronavirus variants, this early hope continues to be misplaced.
While quarantine is effective in preventing the transmission of diseases like SARS and hemorrhagic fevers caused by the Ebola virus, many infectious diseases also have no effective cure.
The term “emerging infectious diseases” is used to describe a variety of modern infectious diseases.
SARS, or Extreme Acute Respiratory Syndrome, is an example of an emerging infectious disease that spread through continents in a matter of weeks thanks to a severe version of the Coronavirus.
Another uncommon but well-known infection caused by prions is mad cow disease, a type of Creutzfeldt-Jakob disease.
The signs and symptoms of each infectious disease are unique. The below are typical signs and symptoms of a variety of infectious diseases:
- Muscle aches
Now, before we get too many complex parts in answering “ What is infectious diseases?”, you have to see a doctor in the following cases:
- If you have been attacked by a dog or a cat
- If you have trouble breathing
- If you’ve Coughed for longer than a week
- If you have a bad headache with a fever
- If you have a rash or swelling
- If you have an unexplained or persistent fever
- If you have had any unexpected eye problems
The history of infectious diseases
Now, if you want to know “what is infectious diseases?”, take a seat and let me tell you a story about the world of diseases we’ve escaped…
What Is Infectious Diseases – In 2019, the world’s average life expectancy was nearing 73 years. It was possibly about 30 in 1800. This is perhaps the most significant historical shift of the past two centuries.
No nation in the world had a life expectancy much higher than 40 in 1800. The World Bank announced the highest numbers for regions in 2018: 84.9 in Hong Kong, 84.9 in Japan, and 84.1 in Macau (the following table).
Life expectancy in chosen countries in 2018 and the United Kingdom in 1900
What Are Infectious Diseases – Today, the majority of people in wealthy countries such as the United Kingdom die of degenerative disorders or their symptoms, such as cancer, heart disease, diabetes, and dementia.
Pneumonia is the only infectious disorder that is still a significant cause of death in wealthy and middle-income countries, primarily as a complication of an underlying chronic disease.
In the past, contagious diseases killed the majority of humans worldwide, and only a small percentage of people survived long enough to succumb to degenerative diseases.
Also, in large famines before the twentieth century, the majority of deaths were caused by infectious diseases, which were triggered by famine-induced behavioral changes.
In today’s high- and middle-income nations, the majority of deaths occur among the aged, while infant and childhood deaths are becoming relatively rare.
What Is Infectious Diseases – Covid19, with the likelihood of a sudden infection leading to severe illness and even death (in a limited number of cases) in adults who are neither elderly nor vulnerable, sounds like a distant echo of an earlier world in which infectious disease death at any age was a constant danger.
Although life expectancy and infant mortality rates differ widely across the world today, nowhere in the world has a lower life expectancy or a higher infant mortality rate than late-Victorian Britain, which has one of the highest life expectancies and infant mortality rates at the time.
What Is Infectious Diseases – In 2018, the child mortality rate (the number of deaths in the first year per thousand live births) ranged from one per thousand in Finland to two per thousand in Japan, Singapore, and Sweden, and four in the United Kingdom, with a mean of 53 across Sub-Saharan Africa.
If we want to know “what is Infectious diseases” between 1876 and 1900, you have to know that 149 out of every thousand babies born in England and Wales, then one of the world’s wealthiest countries, died in their first year of existence.
Surprisingly, the top three spots and seventh position are occupied by high-income East Asian countries, which still seem to have done a good job of containing Covid19 up until the time of publishing.
In terms of life expectancy, Switzerland, Spain, Italy, and Norway lead the European pack.
The United Kingdom is ranked 29th, while Germany is ranked 33rd.
As is well established, the United States, in 49th position, is a global outlier for low results compared to GDP per capita, amid large average health spending, due to gross gaps in access to health care.
What Is Infectious Diseases – As a long-lasting legacy of a very different approach to healthcare access, Cuba is just ahead of the United States in 46th position, despite having much lower income levels.
China, in 69th position, has a life expectancy just 1.8 years lower than the United States and can be predicted to surpass the United States in the not-too-distant future unless the United States drastically changes the healthcare system.
India, ranked 142nd, has a 7.3-year shorter life expectancy than China. Poverty-stricken countries in Sub-Saharan Africa occupy almost all of the bottom 34 places in the global rankings.
What Is Infectious Diseases – And the Central African Republic, which ranks 200th on the list with an average life expectancy of 52.8 in 2018, looks higher than the United Kingdom in 1900, when it had a life expectancy of 46, and much better than England in the early eighteenth century when it had a life expectancy in the mid-thirties.
When we look at mortality before 1900, we can see the underlying essence of this transition.
We have stable awareness of the long-term patterns in mortality and life expectancy in England (but not Wales or Scotland) for nearly five centuries.
That’s much more than any other nation on the globe – thanks to Tony Wrigley, the late Roger Schofield, Jim Oeppen, and the late Ros Davies’ work at the Cambridge Group for the History of Population and Social Structure over many decades.
What Is Infectious Diseases? – Causes, Direct and Indirect Contacts, and the contamination
Now before continuing to know more about “ What is infectious diseases?”, let’s see the causes of the infectious diseases…
- Bacteria: It’s responsible for strep throat, urinary tract infections, and tuberculosis are all caused by these single-celled species.
- Viruses, to be precise. Viruses, which are much smaller than bacteria, are responsible for a wide range of infections, from the common cold to AIDS.
- Fungi is a kind of fungus. Fungi are responsible for a variety of skin disorders, including ringworm and athlete’s foot. Fungi will also affect the lungs and nervous system.
- Parasites are a kind of parasite. Malaria is caused by a parasitic infection spread by mosquito bites. Other parasites can be spread to humans by the feces of animals.
Let’s see how the direct and indirect contact…
What Is Infectious Diseases – Getting into contact with an infected human or animal is a simple way to contract most infectious diseases. Infectious diseases, such as the following, may be transmitted by close contact:
- Individual to individual. Infectious diseases are widely transmitted from one person to another through the direct transmission of bacteria, viruses, or other germs.When a person infected with the bacterium or virus touches, kisses, coughs or sneezes on someone who isn’t infected, this may happen.
These germs can also spread by sexual intercourse due to the exchanging of body fluids. The individual who spreads the germ may not show any signs of the disease and is merely a carrier.
- From animal to human. Being bitten or scratched by an infected animal, even though it is a cat, will make you sick and, in some cases, even kill you.Handling animal waste can also be dangerous. You can contract toxoplasmosis by scooping your cat’s litter box.
- Mother to unborn child Germs that cause infectious diseases may be passed from a pregnant woman to her unborn child.Germs may travel through the placenta or breast milk in some cases. During delivery, germs in the vaginal area may be spread to the infant.
Indirect touch can also spread disease-causing species. An inanimate object, such as a tabletop, doorknob, or faucet handle, can harbor a large number of germs.
What Is Infectious Diseases – When you touch a doorknob that has been touched by someone that is sick with the flu or a cough, for example, you will pick up the germs they left behind.
You can get sick if you then touch your eyes, mouth, or nose before washing your hands.
Bites of insects
Insect vectors, such as flies, fleas, lice, and ticks, help certain germs spread from one host to another. Vectors are the term for these carriers.
Mosquitoes can transmit malaria or the West Nile virus. Lyme disease is caused by a bacterium carried by deer ticks.
Contamination of food
What Is Infectious Diseases – Contaminated food and drink will also flood you with disease-causing germs. This mode of propagation causes germs to propagate to a large number of people from a single source.
For example, the bacterium Escherichia coli (E. coli) can be found in or on some foods, such as undercooked hamburgers or unpasteurized fruit juice.
Now, let’s return to answering our interesting question “What is infectious diseases?”.
What is infectious diseases? – clinical features
Now, focus on me because this will answer a lot if you still wondering “What are infectious diseases?”…
What Is Infectious Diseases – The clinical categories for children younger than 13 years old with HIV infection and the pediatric HIV definition are listed in the 2003 Red Book (Committee on Infectious Diseases, 2003) and the websites of the Centers for Disease Control and Prevention (www.cdc.gov/hiv/pubs.htm).
Acute infectious complications (e.g. bacterial meningitis, CMV retinitis, Toxoplasma gondii encephalitis, and cryptococcosis) and chronic complications (e.g. cumulative multifocal leukoencephalopathy, CNS malignancies, and, most frequently, HIV encephalopathy) distinguish HIV disease in babies and children.
What Is Infectious Diseases – HIV encephalopathy was diagnosed in 178 (23 percent) of 766 children with perinatally acquired AIDS in a multicenter epidemiologic trial in the United States (Lobato et al., 1995).
The median age at encephalopathy diagnosis was 19 months, and it was linked to high morbidity, as demonstrated by repeated hospitalizations, extreme immunodeficiency, and short survival.
HIV encephalopathy is defined as (1) failure to meet or lose developmental milestones or intellectual ability.
What Is Infectious Diseases – As determined by a standard developmental scale or neuropsychological tests; (2) impaired brain growth or acquired microcephaly as determined by head circumference measurements or brain atrophy as determined by computed tomography or magnetic resonance imaging.
Early HIV-1 exposure raises the possibility of a child’s neurodevelopmental problems.
HIV-1 infection was shown to be strongly associated with an elevated risk of all outcome events linked to irregular mental and motor development in the sample.
At the age of four months, there were noticeable differences between the 114 infected and 481 uninfected babies.
The future of infectious diseases
What Is Infectious Diseases – Infectious diseases have been steadily declining in affluent countries over the last century, and these diseases have become minor concerns as opposed to the growing importance of chronic and neoplastic diseases.
With the onset of AIDS and associated diseases such as tuberculosis in the 1980s, this condition began to improve. Other new viruses have emerged, posing serious threats in the future.
The hepatitis C virus is an example of a pathogen that is beginning to affect many peoples’ health and well-being.
What Is Infectious Diseases – While it does not have the same emotional impact as HIV, it is a significant new scourge that would need more efficient management of its dissemination, as well as access to antiviral agents for those who are contaminated (Box 8.4).
Hepatitis C Virus (Box 8.4) (HCV).
The HCV virus was discovered thirteen years after the word “non-A, non-B” hepatitis was coined. HCV was cloned in 1988, years before it was visualized, cultured, or otherwise characterized, marking a watershed moment in molecular virology.
HCV was classified as a distinct genus in the viral family Flaviviridae based on its amino acid sequence and genomic organization.
HCV is an RNA virus that comes in six different genotypes (1–6). In today’s world, intravenous drug use remains the most common cause of infection.
What Is Infectious Diseases – Because of the successful screening procedures in place, transfusion-related HCV is seldom observed. Unlike HBV, transmission from mother to child and sexual transmission is uncommon.
HCV infects almost 170 million individuals worldwide, and it is also the leading cause of liver transplantation in the United States.
Unlike HBV, which causes chronic hepatitis in a small percentage of those infected, HCV causes chronic hepatitis in about 70% of those infected.
HCV, like HBV, is thought to cause hepatic damage as a result of an immune response rather than a direct viral effect.
What Is Infectious Diseases – However, because of inadequate detection (or the money to pay for the above drugs), there is considerable concern that what is being seen at present is only the tip of the iceberg since the virus has a long incubation period, and many who are carriers remain asymptomatic until complications develop.
Age, male sex, alcohol intake, coexisting HIV infection, low CD4+ count, and metabolic disorders such as diabetes all contribute to the growth of liver cirrhosis and, ultimately, hepatocellular cancer.
Excellent serologic or DNA-based assays are available for correct diagnosis, just as they are for HIV.
Predictions of how an individual will respond to antiviral therapy can be made using quantitative RNA assays and genotyping.
Interferon-alpha and ribavirin treatments are successful, particularly for HCV genotypes 2 and 3. (88 percent response rates compared to 48 percent for the other four genotypes).
Without a question, genomics’ promise would open up new avenues to diagnose pathogen infection.
Rather than attempting to identify pathogen-specific nucleic acids, one early model mentioned uses microarrays to detect gene profiles in the patient. Using this method, it was exposed to M.
tuberculosis, a protozoan (Leishmania Donovan), and a worm (Brugia Malay) exposed peripheral blood mononuclear cells displayed distinct expression profiles specific to the infectious agent.
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