Download MBBS (Bachelor of Medicine, Bachelor of Surgery) General Medicine 2022 PPT 7 Rna Viruses Part I Lecture Notes
Infectious diseases
4/5th Semester Classes on Infectious Diseases, 8-9AM, Tuesdays (LT-1)
Topics
1
Approach to Infectious Diseases and their prevention
2
Antibiotic stewardship practices
3
Community-Acquired Infections
4
Health Care?Associated Infections
5
Gram-Positive Bacteria (part-1)
6
Gram-Positive Bacteria (part-2)
7
Gram-Negative Bacteria (part-1)
8
Gram-Negative Bacteria (part-2)
9
Spirochetal Diseases
10
Diseases Caused by Atypical/Miscel aneous Bacterial Infections
11
Revision-cum-exam on bacteria (Must to know type)
12
Infections Due to DNA Viruses
1
13
Infections Due to RNA Viruses (part 1)
14
Infections Due to RNA Viruses (part 2)
15
HIV/AIDS ? part 1
16
HIV/AIDS ? part 2
17
Fungal Infections
18
Parasitic Infections (part 1)
19
Parasitic Infections (part 2)
20
Revision-cum-exam on Virus, Fungal, and Parasite (Must to know type)
Viral Gastroenteritis
? Norovirus may be the second most common viral agent (after rotavirus) among
young children
? By the fecal-oral route but can occur by aerosolization, by contact with
contaminated fomites, and by person-to-person contact
? The stools are characteristically loose and watery, without blood, mucus, or
leukocytes
Enterovirus
? These viruses are not a prominent cause of gastroenteritis.
?3 serotypes of poliovirus,
?21 serotypes of coxsackievirus A,
?6 serotypes of coxsackievirus B1,
?28 serotypes of echovirus,
?enteroviruses 68?71, and
?multiple new enteroviruses (beginning with enterovirus 73)
? Infection is more common in socioeconomical y disadvantaged areas, especially
in those where hygiene is poor
? Transmitted primarily by the fecal-oral or oral-oral route, other rare route also
? IP; 2 to 14 days but usually is <1 week
? After ingestion, it infect epithelial cells in the mucosa of the gastrointestinal tract
and then to spread to and replicate in the submucosal lymphoid tissue, then to
the regional lymph nodes, a viremic phase ensues, and the virus replicates in
organs of the reticuloendothelial system
Most common clinical manifestation
is a nonspecific febrile illness
Poliovirus Infection:
? Abortive poliomyelitis
? Nonparalytic poliomyelitis
? Paralytic poliomyelitis - it is more
common among older
individuals, pregnant women,
and persons exercising
trenuously or undergoing trauma
? Vaccine-associated poliomyelitis
? Postpolio syndrome - a new
onset of weakness, fatigue,
fasciculations, and pain with
additional atrophy of the muscle
group involved during the initial
paralytic disease 20?40 years
earlier
? Isolation of enterovirus in cell culture is the traditional diagnostic procedure
? Identification of the enterovirus serotype is useful primarily for epidemiologic studies
? A pan-enterovirus PCR assay can detect all human enteroviruses
? Intensive supportive care may be needed for cardiac, hepatic, or CNS disease.
? IV, intrathecal, or intraventricular immunoglobulin has been used with apparent
success in some cases for the treatment of chronic enterovirus meningoencephalitis
and dermatomyositis in patients with hypogammaglobulinemia or
agammaglobulinemia.
? Poliovirus is shed from some immunocompromised persons for >10 years, discontinuing
vaccinations is difficult to decide
Viral Respiratory Infections
RHINOVIRUS - In contrast to other picornavirus, rhinoviruses are acid-labile and are
almost completely inactivated at pH 3
? Seasonal peaks in early fal and spring; spread through direct contact with infected
secretions, usually respiratory droplets; IP- 1-2 DAYS
? Antibacterial agents should be used only if bacterial complications such as otitis
media or sinusitis develop
CORONAVIRUS - that infect humans (HCoVs) fall into two genera: Alphacoronavirus
(common cold) and Betacoronavirus (SARS-CoV and MERS-CoV) - it is suspected that
bats may be the animal reservoir
? Person-to-person transmission has been documented; IP ? 2-7DAYS
? SARS usually begins as a systemic illness marked by the onset of fever, which is often
accompanied by malaise, headache, and myalgias and is followed in 1?2 days by a
nonproductive cough and dyspnea, then ARDS in second week
HUMAN RESPIRATORY SYNCYTIAL VIRUS - (HRSV)- A common cold?like syndrome is the
illness most commonly associated with HRSV infection in adults (both upper and lower
respiratory tract illnesses, such as bronchiolitis, croup, and pneumonia)
HUMAN METAPNEUMOVIRUS - (HMPV) - similar to that associated with HRSV
PARAINFLUENZA VIRUS - In older children and adults, parainfluenza infections tend to
be milder, presenting most frequently as a common cold or as hoarseness, with or
without cough
Influenza
? Hemagglutinin is the site by which the virus binds to sialic acid cell receptors, whereas
the neuraminidase degrades the receptor and plays a role in the release of the virus
from infected cells after replication has taken place
? Influenza A viruses are further subdivided (subtyped) on the basis of the surface
hemagglutinin (H) and neuraminidase (N)
? Because the genome is segmented, the opportunity for gene reassortment during
infection is high; reassortment often takes place during infection of cells with more than
one influenza A virus
? Major antigenic variations, called antigenic shifts, are seen only with influenza A viruses
and may be associated with pandemics; Minor variations are called antigenic drifts
? Interpandemic influenza A outbreaks usually begin abruptly, peak over a 2- to 3-week
period, generally last for 2?3 months, and often subside almost as rapidly as they began
? In contrast, pandemic influenza may begin with rapid transmission at multiple locations,
have high attack rates, and extend beyond the usual seasonality, with multiple waves
of attack before or after the main outbreak
? Aquatic birds are the largest reservoir of influenza A viruses; pandemic strains resulted
from reassortment of gene segments between human and avian viruses
? Whereas humans primarily have -2,6-galactose receptors for hemagglutinins and
birds primarily have -2,3-galactose receptors, swine have both types of receptors
? Influenza is most frequently described as a respiratory illness; severe with risk factors
? Pulmonary Complications as PNEUMONIA: "primary" influenza viral pneumonia,
secondary bacterial pneumonia, or mixed viral and bacterial pneumonia
? Myositis, rhabdomyolysis, and myoglobinuria are occasional complications
Measles (Rubeola)
? CDC case definition for measles requires
? (1) a generalized maculopapular rash of at least 3 days' duration;
? (2) fever of at least 38.3?C (101?F); and
? (3) cough, coryza, or conjunctivitis
? IP: is 10 days to fever onset and 14 days to rash onset with Airborne transmission
? D/D: rubella, Kawasaki disease, infectious mononucleosis, roseola, scarlet fever, Rocky
Mountain spotted fever, enterovirus or adenovirus infection, and drug sensitivity
? Serology is the most common method of laboratory diagnosis
? Paradoxical y associated with depressed immune responses to unrelated antigens,
which persist for several weeks to months that enhances susceptibility to secondary
infections with bacteria and viruses that cause pneumonia and diarrhea
Rubella (German Measles)
? Spread from person to person via respiratory droplets
? Primary implantation and replication in the nasopharynx are followed by spread to the
lymph nodes, then other organs or placenta in congenital rubella syndrome
? The pathology of CRS in the infected fetus is well defined, with almost al organs found to
be infected; however, the pathogenesis of CRS is only poorly delineated
? Acquired rubella commonly presents a subclinical and mild disease: a generalized
maculopapular rash that usually lasts for up to 3 days; Lymphadenopathy, particularly
occipital and postauricular, may be noted during the second week after exposure
? The hallmark of fetal infection is chronicity, with persistence throughout fetal
development in utero and for up to 1 year after birth
? Laboratory assessment of rubella infection is conducted by serologic and virologic
methods
? Demonstration of IgM antibodies in an acute-phase serum specimen or a fourfold rise
in IgG antibody (the acute-phase serum specimen should be collected within 7?10
days after onset of illness and the convalescent-phase specimen ~14?21 days after the
first specimen)
? Mature (high-avidity) IgG antibodies most likely indicate an infection occurring at least
2 months previously (This test helps distinguish primary infection from reinfection)
? Symptom based treatment for various manifestations, such as fever and arthralgia, is
appropriate
? Administration of immunoglobulin should be considered only if a pregnant woman
who has been exposed to rubella will not consider termination of the pregnancy under
any circumstance
? The most effective method of preventing acquired rubella and CRS is through
vaccination with an MMR/MMRV (globally RA27/3 virus strain)
Mumps
? Illness characterized by acute-onset unilateral or bilateral tender, self-limited swelling
of the parotid or other salivary gland(s) that lasts at least 2 days and has no other
apparent cause
? Now frequently occurs in older age groups--primarily college students, most of whom
were vaccinated in early childhood
? IP: 19 days (range, 7?23 days); transmitted by the respiratory route via droplets, saliva,
and fomites
? Primary replication likely occurs in the nasal mucosa or upper respiratory mucosal
epithelium; THEN salivary glands, testes, pancreas, ovaries, mammary glands, and
central nervous system (CNS); Other unusual complications include thyroiditis,
nephritis, arthritis, hepatic disease, keratouveitis, and thrombocytopenic purpura
? Typical mumps encephalitis appears to be secondary to respiratory spread and is
probably a parainfectious process
? Mumps parotidits, usually within 24 h of prodromal viral symptoms
? Detection of viral RNA by RT-PCR or on serology
? Therapy for parotitis and other clinical manifestations is symptom based and
supportive
? Treatment consists of general supportive measures, such as hydration and
administration of antipyretic agents
? Prompt antibiotic treatment for patients who have clinical evidence of bacterial
infection; Streptococcus pneumoniae and Haemophilus influenzae type b are
common causes of bacterial pneumonia following measles
? Once-daily doses of 200,000 IU of vitamin A for 2 consecutive days to all children
with mea
? Most complications of measles involve the respiratory tract (croup, Giant-cell
pneumonitis, Otitis media, and bronchopneumonia) and include the effects of
measles virus replication itself and secondary bacterial infectionsles who are 12
months of age
? Postmeasles encephalomyelitis - within 2 weeks of rash onset and is characterized
by fever, seizures, and a variety of neurologic abnormalities
? Measles inclusion body encephalitis (MIBE- occurs months after infection) and
subacute sclerosing panencephalitis (SSPE- occurring 5?15 years after measles)
? Prophylaxis with immunoglobulin is recommended for susceptible household and
nosocomial contacts who are at risk of developing severe measles, particularly
children <1 year of age, immunocompromised persons (including HIVinfected
persons previously immunized with live attenuated measles vaccine), and pregnant
women
Thank you
This post was last modified on 05 April 2022