NURS 2550H Chapter Notes - Chapter 3: Pepsin, Microvillus, Appendicitis
26 Jun 2018
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NURS 2550 Sept 25th 2017
WEEK 3 READINGS
Chapter 15- Viral Infections
- Not all infections of cells cause disease, and such infections might not be apparent
because of the lack of symptoms
- Most virions that can reach the lungs are destroyed by alveolar macrophages
- 90% of acute upper respiratory and 50% of lower respiratory infections are caused by
viruses
Common Cold
- mild and self-limiting
- the most frequent of all human diseases and typically lasts 3-5 days
- symptoms: rhinitis (inflammation of the mucous membrane of the nose), runny nose,
nasal congestion, sneezing, sore throat, cough, headache…
- the common cold is a trigger for asthmatic symptoms in children with asthma
- children average 3-8 common colds a year, adults average 2-4 a year
- highly contagious and rapidly spreading
- transmission can occur through aerosols, but most commonly spreads through
contaminated hands or fomites
- most contagious for the first 2-3 days
- generally, contagion free by day 7-10
- rest and lots of fluids help alleviate symptoms
- antibiotics should not be used to treat the common cold due to its viral origin
Influenza
- primary causes for epidemics and endemic diseases of the respiratory system
- caused by orthomyxoviruses
- they are RNA viruses designated as types a, b and c
- spread through coughing or sneezing, or by fomites and then by hand from touching the
mouth, nose or eyes
- influenza viruses’ A and C can infect many species whereas virus B is only capable of
infecting humans
- Type A is the most virulent and causes the most severe disease state
- because influenza viruses kill epithelial cells, the first line of defense is breached and flu
patients become more susceptible to bacterial infections
- virus-induced immune suppression occurs
- the influenza genome is not a single piece of nucleic acid but instead consists of 8 pieces
of segmented negative-sense RNA, encoding 11 proteins
o2 of these proteins, hemagglutinin and neuraminidase (large glycoproteins) are
found on the outside of the viral particles
oHemagglutinin: a lectin that mediates the binding of the virus to target cells and
the subsequent entry of the viral genome into the host
oNeuraminidase: an enzyme involved in the release of the progeny (replicated)
viruses from infected cells
oAfter the release of the newly produced influenza viruses the host cell dies
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NURS 2550 Sept 25th 2017
- New influenza virus variants (strains) are the result of frequent antigenic changes (i.e.
antigenic drift) resulting from point mutations during viral replication.
othese rapid mutations are partially due to the absence of RNA-proofreading
enzymes
oas a result, RNA-dependent RNA transcriptase makes a single-nucleotide
insertion error about once every 10000 nucleotides, making almost every newly
formed influenza virus a potential mutant
oinfluenza B viruses undergo antigenic drift less frequently than the influenza A
viruses
- symptoms: fever, headache, fatigue, dry cough, sore throat, runny or stuffy nose,
muscle aches, gastrointestinal symptoms (nausea, vomiting, diarrhea)
- complications: bacterial pneumonia, ear infections, sinus infections, dehydration,
worsening of chronic existent medical conditions such as asthma, diabetes or congestive
heart failure
- the annual “flu shot” is the primary method for preventing the flu and its possible
complications
- vaccination can prevent hospitalization and death among people at risk (the very young,
the elderly, and those with compromised immune systems)
- will reduce flu-associated respiratory illnesses among people of all age-groups
Viral Pneumonia
- symptoms: fever, nonproductive cough, rhinitis (inflammation of mucous membranes of
the nose), myalgia (muscle pain), headache.
- Most cases are mild and fade away on their own within 1-3 weeks
- More serious cases may require hospitalization and people typically at risk are those
with impaired immune systems
- Antibiotics are ineffective
- The more serious forms can be treated with antiviral meds
- Complications: respiratory failure, heart failure, liver failure, and sometimes bacterial
infections can follow viral infection, resulting in a more serious form of pneumonia
Hantavirus Pulmonary Syndrome
- Deadly disease caused by a group of viruses called hantaviruses
- Carried by rodents, and humans can contract the disease when they encounter infected
rodents, their urine, or their droppings
- Person-to-person transmission has not been reported
- At first appears like a severe cold or influenza and quickly progresses to severe
respiratory difficulties, with fatalities occurring in 30-40% of cases
- Acute respiratory distress syndrome (ARDS): gas exchange and therefore O2 uptake in
the lungs is severely impaired compromising the functionality of all organs of the body
- The main treatment for ARDS is mechanical ventilation
Severe Acute Respiratory Syndrome (SARS)
- Caused by SARS coronavirus
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NURS 2550 Sept 25th 2017
- Originated in mainland China (2002)
- Transmitted by close person-to-person contact, respiratory droplets depositing on the
mucous membranes of a nearby individual
- Can be life-threatening
- Symptoms: high fever, headache, body aches, dry cough, followed by pneumonia,
sometimes diarrhea
- Symptoms usually appear 2-10 days after exposure
- In most cases symptoms appear within 2-3 days and abt. 10-20% of cases require
mechanical ventilation
- Antipyretics, O2, and additional ventilation support is the only treatment available to
date
Chapter 16-Infections of the GI system
- The GI tract is a common and easily accessible portal of entry for microbes or their
toxins, with the ability to cause infection, inflammation, and/or disease
- Major concern worldwide
- Contaminated food, water, and fomites, if they gain access through the fecal-oral route,
all can infect the GI system
- P.320-322 Table 16.1
- The GI tract does not have a dead layer of cells as the skin does and therefore it is not as
efficient a defense mechanism
- It does provide a moist and warm environment perfect for microbial growth
- The GI tract has a normal flora that also helps to protect against pathogens via
competition
Resident Microbial Flora
- The GI tract resident (normal) microbial flora is a complex and diverse ecosystem
containing a large collection of microorganisms that flourish in the nutrient-rich
environment provided by the digestive system
- The flora may prevent infection by competing or interfering with pathogens or
potentially pathogenic organisms
- Increasing numbers or organisms as one moves from the upper GI to the large intestine
- Antibiotics that upset the balance of the normal flora may favor infections by exogenous
pathogens and the overgrowth of endogenous pathogens
- Recovering patients who have taken antibiotics are advised to consume products such
as yogurt or take probiotic capsules to replenish the normal gut flora that may have
been decimated by the antibiotics
- Oral cavity:
oMore then 700 species of bacteria
oAt birth the oral cavity is sterile but rapidly becomes colonized by organisms
from the environment especially after the first breast feed
- Stomach:
oContains few bacteria because of its high acidity
oRelatively hostile environment for bacteria
3
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Document Summary
Not all infections of cells cause disease, and such infections might not be apparent because of the lack of symptoms. Most virions that can reach the lungs are destroyed by alveolar macrophages. 90% of acute upper respiratory and 50% of lower respiratory infections are caused by viruses. Most contagious for the first 2-3 days generally, contagion free by day 7-10 rest and lots of fluids help alleviate symptoms antibiotics should not be used to treat the common cold due to its viral origin. Will reduce flu-associated respiratory illnesses among people of all age-groups. Viral pneumonia symptoms: fever, nonproductive cough, rhinitis (inflammation of mucous membranes of the nose), myalgia (muscle pain), headache. Most cases are mild and fade away on their own within 1-3 weeks. More serious cases may require hospitalization and people typically at risk are those with impaired immune systems. The more serious forms can be treated with antiviral meds.
