virus pathogenicity, symptoms and disease Flashcards
Virus pathogenicity
the ability of a virus to cause disease
Not all viruses are pathogenic, some are pathogenic under certain conditions.
Viral disease
a sum of the effects on the host arising form virus replication and the immune response
subclinical or asymptomatic infections
Infections that do not result in disease are known as subclinical or asymtomatic
Symptoms arising from virus infection may vary from asymtomatic, mild, moderate and acute, depending on a number of factors such as virus virulence, viral dose, host immune status, etc.
Adenoviruses
- They are medium-sized (90-100 nm), non-enveloped icosohedral viruses with double-stranded DNA.
- More than 50 types of immunologically distinct adenoviruses can cause infections in humans.
- Adenoviruses are relatively resistant to common disinfectants and can be detected on surfaces, such as doorknobs, objects, and water of swimming pools and small lakes
Adenovirus transmission
- Adenoviruses are usually transmitted from infected people to others through:
- close personal contact such as touching or shaking hands
- the air by coughing and sneezing
- touching objects or surfaces with adenoviruses on them then touching your mouth, nose, or eyes.
Adenovirus symptoms
Adenoviruses symptoms are:
• common cold or flu-like symptoms
• fever
• sore throat
• acute bronchitis (inflammation of the airways of the lungs, sometimes called a “chest cold”)
• pneumonia (infection of the lungs)
• pink eye (conjunctivitis)
• acute gastroenteritis (inflammation of the stomach or intestines causing diarrhea, vomiting, nausea
and stomach pain).
• less commonly, neurological disease.
• People with weakened immune systems are at high risk for developing severe illness caused by adenovirus infection.
• Some people infected with adenoviruses, especially those who have weakened immune systems, can have ongoing infections in their tonsils, adenoids, and intestines that do not cause symptoms. They can shed the virus for weeks or longer.
• Prevention of adenoviruses is through vaccine administration
Varicella (chickenpox)
• Varicella, commonly called chickenpox is an acute infectious disease.
• It is caused by varicella-zoster virus (VZV), which is a DNA virus that is a member of the family
herpesviridae
Varicella (chickenpox)
Transmission
Transmission can occur through contact, inhalation of aerosols from vesicular fluid from skin lesions
Varicella (chickenpox)
disease and infection
• Disease: After the primary infection, VZV stays in the body (in the sensory nerve ganglia) as a latent
infection
- Primary infection with VZV causes varicella (chickenpox).
- Reactivation of latent infection causes herpes zoster (shingles or painful rash)
Varicella (chickenpox)
symptoms
- Primary infection with VZV causes varicella (chickenpox).
- Reactivation of latent infection causes herpes zoster (shingles or painful rash).
- The rash is generalized and pruritic (itchy).
- It progresses rapidly from macular to papular to vesicular lesions before crusting.
- Lesions are typically present in all stages of development at the same time.
- The rash usually appears first on the chest, back, and face, then spreads over the entire body.
- The lesions are usually most concentrated on the chest and back.
- Symptoms typically last 4 to 7 days.
Varicella (chickenpox)
incubation period
• Incubation Period
• The average incubation period for varicella is 14 to 16 days after exposure to a varicella or a herpes zoster rash, with a
range of 10 to 21 days.
• Early symptoms of mild fever and malaise may occur 1 to 2 days before rash onset, particularly in adults. In children, the
rash is often the first sign of disease
Varicella (chickenpox)
complications
• Complications
• The most common complications from varicella are:
• In children: Bacterial infections of the skin and soft tissues
• In adults: Pneumonia (lung inflammation, pus filling the air sacs)
• Severe complications caused by the virus include cerebellar ataxia, encephalitis, viral pneumonia, and hemorrhagic
conditions. Other severe complications are due to bacterial infections and include:
• Septicemia (Blood poisoning by bacteria)
• Toxic shock syndrome (condition due accumulation of pathogenic toxins)
• Necrotizing fasciitis (rare bacteria infection)
• Osteomyelitis
• Bacterial pneumonia
• Septic arthriti
Herpes zoster virus
Herpes zoster, also known as shingles (painful rash), caused by the reactivation of
the varicella-zoster virus (VZV), the same virus that causes varicella (chickenpox)
Herpes zoster virus
symptoms
Primary infection with VZV causes varicella. Once the illness resolves, the virus
remains latent in the dorsal root ganglia (neurons). VZV can be reactive later in a
person’s life and cause a painful, maculopapular rash called herpes zoster.
• The rash is usually painful, itchy, or tingly. These symptoms may precede rash
onset by several days. Some people may also have headache, photophobia
(sensitivity to bright light), and malaise in the prodromal phase.
• The rash develops into clusters of vesicles. New vesicles continue to form over
three to five days and progressively dry and crust over. They usually heal in two to
four weeks. There may be permanent pigmentation changes and scarring on the
skin.
Herpes zoster virus
vaccine
• Vaccine: Recombinant zoster vaccine (RZV, Shingrix) is the recommended vaccine
to prevent shingles and its complications.
Conjunctivitis (Pink eye)
People often refer to conjunctivitis “pink eye” because it can cause the white of the eye to take on a pink
or red color.
• Symptoms of pink eye can vary but typically include redness or swelling of the white of the eye
Conjunctivitis (Pink eye)
viral causes
Cause: An array of viruses can cause viral conjunctivitis, with adenoviruses being one of the most common
causes:
• Adenoviruses
• Rubella virus
• Rubeola (measles) virus
• Herpesviruses, including
• Herpes simplex virus
• Varicella-zoster virus, which also causes chickenpox and shingles
• Epstein-Barr virus, which also causes infectious mononucleosis (mono)
• Picornaviruses, such as coxsackievirus A24 and enterovirus 70 (which has caused outbreaks in other
countries
Conjunctivitis (Pink eye)
transmission
• Viral conjunctivitis is highly contagious. Most viruses that cause conjunctivitis spread through hand-to-eye contact by hands or objects that are
contaminated with the infectious virus.
• Having contact with infectious tears, eye discharge, fecal matter, or respiratory discharges can contaminate hands. Viral conjunctivitis can also
spread by large respiratory tract droplets. As viral conjunctivitis can be highly contagious, infected individuals should be counseled to prevent
transmission e.g., washing hands frequently, using separate towels, and avoiding close contact with others during the period of contagion.
• Most cases of acute, infectious conjunctivitis in adults are viral and self-limited; these cases do not require antimicrobial treatment.
• Antiviral medication may be used to treat more serious forms of conjunctivitis, such as conjunctivitis caused by herpes simplex virus or
varicella-zoster virus.
Conjunctivitis (Pink eye)
symptoms
• Symptoms: Depending on the cause of viral conjunctivitis, some patients may have additional symptoms or conditions, such as the following:
Common cold, flu, or other respiratory infection
Conjunctivitis (Pink eye)
Pharyngoconjunctivial fever
• Pharyngoconjunctivial fever – a syndrome that can produce conjunctivitis as well as a fever and sore throat, and is most commonly caused by
infection with adenovirus serotypes 3, 4, and 7
.
Conjunctivitis (Pink eye)
Epidemic keratoconjunctivitis
• Epidemic keratoconjunctivitis – a more severe type of conjunctivitis, commonly caused by infection with adenovirus serotypes 8, 19, and 37
Conjunctivitis (Pink eye)
Acute hemorrhagic conjunctivitis
• Acute hemorrhagic conjunctivitis – a type of conjunctivitis that is often associated with large epidemics worldwide, especially in the tropical
and subtropical regions. The viruses most commonly associated with it include enterovirus 70, coxsackievirus A24, and adenoviruses.
Conjunctivitis (Pink eye)
Herpetic keratoconjunctivitis
• Herpetic keratoconjunctivitis – a type of conjunctivitis associated with herpes simplex virus and blister-like lesions on the skin; it may affect
only one eye.
Conjunctivitis (Pink eye)
Rubella and rubeola (measles)
• Rubella and rubeola (measles) – conjunctivitis can occur with these viral rash illnesses which are usually accompanied by rash, fever, and
cough
Cytomegalovirus (CMV)
• CMV is a member of the herpesvirus family, which includes herpes simplex virus types 1 and 2, varicella-
zoster virus, and Epstein-Barr virus.
Cytomegalovirus (CMV)
transmisson
• Transmission: by direct contact with infectious body fluids, such as urine, saliva, blood, tears, semen, and
breast milk.
• CMV can be transmitted sexually and through transplanted organs and blood transfusions.
• CMV, is a common virus that infects people of all ages. Over half of adults have been infected with CMV by
age 40.
Cytomegalovirus (CMV)
symptoms
• Symptoms: Most people infected with CMV show no signs or symptoms.
Cytomegalovirus (CMV)
congenital cmv
• Congenital CMV: Occurs when a baby is born with cytomegalovirus (CMV) infection. About one out of
every 200 babies is born with congenital CMV infection. About one in five babies with congenital CMV
infection will have long-term health problems.
Cytomegalovirus (CMV)
prevention
• Prevention: CMV is common in children and can be found in especially high amounts in young children’s
saliva and urine. Avoiding contact with saliva and urine from young children might reduce the risk of CMV
infection.
• No treatment exist currently.
Epstein-Barr virus (EBV)
symptoms
- EBV, is one of the most common human viruses in the world. It spreads primarily through saliva.
- EBV infection could result in mononucleosis (kissing disease) and symptoms include:
- extreme fatigue
- fever
- sore throat
- head and body aches
- swollen lymph nodes in the neck and armpits
- swollen liver or spleen or both
- rash
Epstein-Barr virus (EBV)
pathology
Pathology: EBV can cause infectious mononucleosis, also called mono, and other illnesses. Infection
in most persons with EBV may persist in their lifetime without symptoms.
• Mono caused by EBV is most common among teens and adults.
• People with weakened immune systems may develop more severe symptoms and complications
from EBV infection. Also, they may experience more severe illness due to EBV infection.
Epstein-Barr virus (EBV)
nervous disorder
- Nervous disorder
- EBV infection can affect a person’s brain, spinal cord, and nerves resulting in conditions such as:
- Viral meningitis (swelling of the tissues that cover the brain and spinal cord)
- Encephalitisexternal icon (swelling of the brain)
- Optic neuritisexternal icon (swelling of the eye nerve)
- Transverse myelitisexternal icon (swelling of the spinal cord)
- Facial nerve palsiesexternal icon (paralysis of facial muscles)
- Guillain-Barré syndrome (an immune system disease)
- Acute cerebellar ataxiaexternal icon (sudden uncoordinated muscle movement)
- Hemiplegia (paralysis on one side of the body)
- Sleep disorders
Epstein-Barr virus (EBV)
hematological system
• Hematological System
• EBV infection can affect a person’s blood and bone marrow. The virus
can cause the body to produce an excessive number of white blood
cells called lymphocytes (lymphocytosis).
• EBV can also weaken the immune system, making it more difficult for
the body to fight infection
Epstein-Barr virus (EBV)
cancers
Cancers associated with EBV infection include:
• Burkitt’s lymphomaexternal icon (cancer of the lymphatic system)
• Nasopharyngeal carcinomaexternal icon (cancer of the upper throat)
• Hodgkin’s diseaseexternal icon and non-Hodgkin’s lymphomaexternal icon (cancers of the lymphatic system)
• Post-transplant lymphoproliferative disorder (white blood cells are produced in excess)
• Other tumors including leiomyosarcomas (cancer in the soft tissue) and T-cell lymphoma
Epstein-Barr virus (EBV)
complications
Complications of EBV infection include:
• Acute bacterial sinusitisexternal icon (bacterial infection of the sinus cavities)
• Suppurative lymph nodes (swelling of lymph nodes)
• Mastoiditisexternal icon (bacterial infection of the mastoid bone of the skull)
• Sialadenitisexternal icon (swelling and injury of salivary glands)
• Blockage of the air passages in the nose and throat
Measles
taxonomy and history
- Measles virus has a single strand negative-sense RNA, belonging to the family Paramyxoviridae.
- It can lead to serious health complications in humans, or even death.
- In 2019, the estimated number of measles cases was over 9 million people, resulting in the death of 207,500 people (mostly children).
- The health consequences of measles infection can be lifelong, including economic losses for individuals, families and societies.
- Measles are amongst the “vaccine-preventable diseases” (VPD). Implying that if vaccine is delivered on schedule and as recommended, it can keep people from catching and giving these diseases to others