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Microbiology > Diseases exam 2 > Flashcards

Diseases exam 2 Flashcards

1
Q

What is the infectious agent of rubella?

A

Rubella virus. It is a single stranded RNA enveloped virus

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2
Q

Taxonomy of rubella

A

It is a member of the togavirus family and a member of the genus Rubivirus

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3
Q

Transmission of rubella

A

Transmission is person to person. It is transmitted by nasal secretions shortly before and for about a week after the rash appears. The virus is highly infectious

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4
Q

Rubella

A

Also known as German measles. It is the mildest of the rash causing viral diseases, but can severely impact a fetus. Prior to the vaccine nearly everyone caught rubella, 50% of cases in children and 90% cases are not recognized

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5
Q

Incubation period of rubella

A

14-21 days, on average about 18 days

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6
Q

Rubella prodromal illness

A

In adults, there may be a prodromal illness preceding the rash by 1-7 days. People may feel tired, have a headache and fever, have a mild sensitivity to light, conjunctivitis, swollen cervical lymph nodes that occur before rash

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7
Q

Rubella symptoms

A

Rash appears first on the trunk after 16-21 days after infection- characterized by a mild maculopapular rash. Other symptoms are swollen lymph nodes, fever, sore throat, and feeling tired

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8
Q

Complications of rubella

A

Arthritis may occur in up to 70% of adult women who are infected. Testicular swelling occurs mainly in adults, but can make males infertile. Other complications include inflammation of nerves, encephalitis, congenital rubella syndrome, and miscarriage

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9
Q

Pathogenesis of rubella

A

When the virus enters the body, it replicates in the upper respiratory tract and will spread in the bloodstream to the lymphoid tissues, skin, and other organs. The cellular immune response is thought to play a role on the rash and the arthritis symptoms

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10
Q

Diagnosis of rubella

A

Collect throat (best source), nasal, or urine specimens for viral detection by PCR testing or molecular testing. IgM and IgG antibody titration can be done on blood samples. Clinical diagnosis of rubella (based only on the symptoms) is unreliable- up to half of all infections can be subclinical

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11
Q

Treatment of rubella

A

No current official treatment is available

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12
Q

How can rubella be prevented?

A

Vaccination- MMR combined attenuated vaccine. One dose of MMR vaccine is about 97% effective at preventing rubella if exposed to the virus

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13
Q

How does rubella harm a developing fetus?

A

Caused by rubella virus induced cellular damage and the effect of the virus on dividing cells. Rubella virus is likely transported into the fetal circulation as infected endothelial cell emboli, which can result in infection and damage of fetal organs. The virus can induce damage by apoptosis, probably due to how the virus replicates

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14
Q

When is the risk of congenital rubella syndrome highest?

A

In the first trimester. The range of abnormalities is correlated with gestational age during maternal rubella infection in the first trimester. If maternal infection occurs after the first trimester, the frequency and severity of fetal damage decreases drastically. This is probably because the fetus has developed humoral and cell mediated immune responses at this point, and has passively received maternal antibodies

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15
Q

Symptoms of congenital rubella syndrome

A

The triad of congenital rubella syndrome is cataracts, heart defects, and deafness- these defects can be temporary or permanent. In infants with CRS, rubella virus continues to replicate and be excreted. This means that contacts with the infant can be infected

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16
Q

How is congenital rubella syndrome diagnosed?

A

Rubella IgG and IgM antibodies synthesized by the fetus are detectable at birth in CRS. Diagnosis is made using IgM responses since maternal IgG antibodies are present in the infants’ sera. The virus is secreted in infants with CRS, but it declines progressively in the first year

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17
Q

What is the replication number for rubella?

A

The R0 for rubella is 3-8, but can be as high as 12 in crowded, developing countries

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18
Q

What is the herd immunity threshold for rubella in the US?

A

In the US, the herd immunity threshold is 85-88%. Rubella may be easier to eradicate than measles due to its lower R0 value

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19
Q

Why is rubella virus a candidate for global eradication? (3)

A
  1. Humans are the only known host
  2. Accurate diagnostic and molecular assays exist
  3. There has been demonstrated sustained interruption of endemic transmission in the Americas since 2009
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20
Q

For thousands of years, how did people think malaria was contracted?

A

For over 2500 years, the idea that malaria fevers were caused by miasmas rising from swamps persisted. The association was because malaria is more common in humid areas- these areas and swamps attracted mosquitos. The world malaria comes from the Italian mal’aria- bad air

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21
Q

Charles Louis Alphonse Laveran

A

First described the malaria parasite

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22
Q

Malaria is caused by a

A

Protozoan

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23
Q

Infectious agents of malaria (5)

A
  1. Plasmodium falciparum
  2. Plasmodium vivax- causes 77% of the infections in the Americas
  3. Plasmodium malariae
  4. Plasmodium ovale
  5. Plasmodium knowlesi- most recent, found in Oceania
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24
Q

Plasmodium falciparum

A

Most deadly and most common in general. Most of the deaths occur in Africa, and this agent is only found in Africa. Resistant to most antimicrobials. Causes the most severe cases of anemia, a common cause of death

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25
Q

Where is malaria common?

A

Common in developing countries and areas with warm temperatures and high humidity. It is rare in the US, but more common in Africa, central and south America, Dominican Republic, Haiti, and other areas in the Caribbean, Eastern Europe, South Asia, and islands in the Central and South Pacific Ocean (Oceania)

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26
Q

How is malaria transmitted?

A

Via a mosquito vector. 2 hosts are needed for the parasite to survive- humans and mosquitoes

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27
Q

Hypnozoite

A

Dormant form in the liver of only certain forms of the parasite. You can’t give blood if you acquire malaria for this reason. A hypnozoite can leave the liver cells and reproduce under certain conditions

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28
Q

How does a mosquito transmit the malaria parasite to a host?

A

Mosquitoes take a blood meal and inject sporozoites (this is the cell that can infect new hosts). They develop in the salivary glands of the mosquito and are released when the mosquito has a blood meal

29
Q

What happens to malaria sporozoites when they enter a human?

A

Once they enter the human, they migrate to and enter the cells of the liver, and then they multiply by sexual reproduction. They form a schizont that will rupture once it is full of sporozoites. Once the schizont ruptures, it releases what are considered merozoites into the bloodstream

30
Q

Malaria blood cycle

A

Begins when merozoites enter the bloodstream and infect red blood cells. The merozoites begin reproducing in the red blood cells and go through a ring stage, which will eventually become trophozoites.

31
Q

Malaria liver cycle

A

The sporozoites multiply in the liver by sexual reproduction. They form a schizont that will rupture once it is full of sporozoites. Once the schizont ruptures, it releases what are considered merozoites into the bloodstream. However, the liver cycle can continue at the same time as the blood cycle. The sporozoites can continue to infect liver cells and cause them to rupture. Sometimes, the schizont in the liver never ruptures. In this case, red blood cells will contain the schizont which will become dormant for many years. They can cause malaria relapses in the future.

32
Q

2 cycles that immature trophozoites go through

A
  1. The immature trophozoites will become mature and eventually divide into schizonts, the schizont will rupture and infect another red blood cell, and the cycle continues
  2. The immature trophozoites can also be converted into gametocytes and go through a sexual erythrocytic stage.
33
Q

Merozoites

A

The cell that is produced when the sporozoites multiply by forming a schizont. The merozoites have a cell membrane and cytoplasm. The merozoites begin reproducing in the red blood cells and go through a ring stage, which will eventually become trophozoites

34
Q

Sexual erythrocytic stage of malaria

A

The gametocytes mature in humans, but they do not fuse there. When a mosquito takes a blood meal, it ingests a female macrogametocyte and a male microgametocyte. The gametocytes travel to the stomach of the mosquito
The microgametes are the ones with a flagella, and they will fuse with the macrogametes. Once they fuse, they form an ookinete, which is similar to the human equivalent of an egg. Ookinetes can elongate and invade the gut wall of the mosquito, where they will undergo sexual reproduction into an oocyst

35
Q

How is malaria transmitted in the US?

A

By a mosquito vector. Sometimes, people who have traveled abroad will accidentally transport infected mosquitoes on their luggage. Congenital malaria can be transmitted from mom to fetus during pregnancy. It can also be transmitted through blood transfusion, although this is rare in the US

36
Q

Incubation period of malaria

A

Incubation period is typically 10 days to 1 month but can be 1 year or more. There is a wide spectrum of disease ranging from asymptomatic carrier state to death

37
Q

Symptoms of uncomplicated malaria (6)

A
  1. Fever and sweating
  2. Chills that shake the whole body
  3. Headache and muscle aches
  4. Fatigue
  5. Chest pain, breathing problems, and cough
  6. Diarrhea, nausea, and vomiting
38
Q

Symptoms of complicated malaria (4)

A
  1. Anemia- occurs mainly in children and is commonly how people die
  2. Anabolic acidosis and jaundice- can cause hepatitis
  3. Organ failure
  4. Cerebral malaria
39
Q

Cerebral malaria

A

Accounts for 80% of fatal malaria cases- Plasmodium falciparum causes this most commonly. It presents as altered mental status, violent behavior, headache, and very high fever. Can cause coma, seizures, and death. Results in cerebral edema and increased brain volume

40
Q

How is malaria diagnosed?

A

Through direct methods- microscopic analysis, rapid diagnostic test (checks if the person has antigens), molecular tests. Can also be diagnosed through indirect methods- immunofluorescence or ELISA

41
Q

Treatment of malaria

A

There are multiple types of drugs. Chloroquine, Doxycycline, Atovaquone, Mefloquine, Quinine. Artemisinin drugs (artemether and artesunate)- mostly commonly used and most effective against multiresistant malaria

42
Q

Malaria prevention (5)

A
  1. Apply mosquito repellent with DEET to exposed skin
  2. Drape mosquito netting over beds- carrier mosquitoes are most active at night
  3. Put screens on windows and doors
  4. Treat clothing, mosquito nets, tents, sleeping bags, and other fabrics with an insect repellent called permethrin
  5. Wear long pants and long sleeves to cover your skin
  6. If you travel to areas where malaria is endemic, preventive medication is available
43
Q

Malaria vaccine

A

Mosquirix was approved in 2015. It requires 4 doses and prevents 4 out of 10 malaria cases and 3 out of 10 cases of severe malaria. Cuts the level of severe anemia by 60%- therefore prevents many deaths

44
Q

Which mosquitoes spread malaria?

A

Spread by female Anopheles mosquitoes

45
Q

Coronaviruses

A

Typically affect the respiratory tracts of birds and mammals, including humans. Associated with the common cold, bronchitis, pneumonia, severe acute respiratory syndrome, and can affect the gut

46
Q

Infectious agent of SARS-CoV-2

A

Coronaviridae. It is enveloped, spherical, or pleomorphic, and is a positive single stranded RNA virus. Viral particles contain characteristic spikes- club or petal shaped resembling a solar corona

47
Q

Which receptors does coronavirus bind to?

A

ACE2 receptors. They are found in the brain, esophagus, lungs, stomach, gallbladder, liver, colon, kidneys, lungs, heart and vasculature, and the small intestines

48
Q

How can coronavirus infection affect the organs?

A

In the lungs (epithelial cells and type 2 alveolar cells), COVID-19 infection can cause ARDS and respiratory failure. Infection in the heart (cardiomyocytes) can cause myocardial infarction, heart failure, myocarditis, and arrhythmia. Infection in the vasculature (endothelial cells and smooth muscle cells) can cause endothelial dysfunction, vascular inflammation, micro/macrovascular thrombosis, and vasospasm

49
Q

Coronavirus replication cycle (8)

A
  1. Binding and viral entry via membrane fusion or endocytosis
  2. Release of viral genome
  3. Translation of viral polymerase protein
    RNA replication
  4. Subgenomic (nested) transcription
  5. Translation of viral structural proteins- S, M, and E proteins at the ER membrane
  6. S, E, and M proteins combine with nucleocapsid
  7. Formation of mature virion
  8. Exocytosis
50
Q

How is coronavirus transmitted?

A

Transmitted from person to person through aerosols. People can breathe in droplets or by touching a surface with droplets and then touching their eyes, nose, or mouth. It can also be transmitted from fomites or from animals to people

51
Q

Variant

A

A variant is a viral genome that may contain one or more mutations. Some variants are more transmissible than others. The delta variant has a greater R0 value (5-9) than the alpha variant (4-5). The most successful variants are the ones that spread as quickly as possible before detection (before they can be stopped by quarantine or other measures)

52
Q

How do coronavirus variants originate?

A

All viruses mutate over time. As SARS-CoV-2 replicates in the cell, it has the potential to change slightly. Most of the time, these changes don’t impact the properties of the virus. However, sometimes a mutation will impact a property like transmission.

53
Q

Variant of interest (VOI)

A

A SARS-CoV-2 variant with genetic changes that are predicted/known to affect transmissibility, disease severity, immune escape, diagnostic escape, or therapeutic escape.

54
Q

Variant of concern (VOC)

A

A SARS-CoV-2 variant meeting the definition of a VOI and associated with one or more of the following changes at a global level: increased transmissibility, detrimental change in epidemiology, increase in virulence, change in clinical disease presentation, decrease in effectiveness of public health measures or therapeutics

55
Q

R0

A

Defined as the average number of secondary cases of an infectious disease arising from a typical case in a totally susceptible population. It can also be estimated by including pre-existing immunity in the population. It can be used to determine the herd immunity threshold and the immunization coverage needed to protect against disease

56
Q

Incubation period of covid

A

Typically 10-14 days. A person is contagious 3-5 days before symptoms are present. Asymptomatic carriers are common, particularly in people below 30 years old

57
Q

Symptoms of covid

A

May appear 2-14 days after exposure to the virus. Fever or chills, cough, shortness of breath, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea

58
Q

Viral load

A

The amount of virus that builds up in someone’s body. The alpha and delta variants have a peak viral load at 3 days after infection. The virus cleared up 9 days after infection
Omicron has the same of slightly lower average viral load, but the infection cleared one day sooner than delta

59
Q

Emergency warning signs for COVID-19 (5)

A
  1. Trouble breathing
  2. Persistent pain or pressure in the chest
  3. New confusion
  4. Inability to wake or stay awake
  5. Bluish lips or face
60
Q

Covid outcomes

A

Most people (about 80%) recover from the disease without needing special treatment. Older people, and those with underlying medical problems like high blood pressure, heart problems or diabetes, are more likely to develop serious illness. About 2% of people with the disease have died

61
Q

Covid complications (3)

A
  1. Severe pneumonia which can lead to death
  2. 1 out of every 6 people becomes seriously ill and develop difficulty breathing
  3. Multisystem inflammatory syndrome (MIS-C) is a rare complication following infection in children
62
Q

Post-COVID conditions (long COVID)

A

Wide range of new, returning, or ongoing health problems experienced for 4 or more weeks after infection with SARS-CoV-2 virus. Symptoms include regular COVID symptoms, and/or: post exertional malaise, brain fog, heart palpitations, pins and needles, sleep problems, lightheadedness, rash, mood changes, or changes in menstrual cycles

63
Q

Viral diagnostic tests for covid (3)

A
  1. Nucleic acid amplification tests (NAATs)
  2. Lab test- real time reverse transcriptase (RT-PCR) diagnostic panel for the presence of viruses, takes days
  3. Rapid test- takes minutes, includes antigen and some NAATs. Self tests fall under this category
64
Q

Antibody or serological covid tests

A

Use a blood sample. Done to detect the presence of IgG and IgM antibodies, developed in response to past infection. Not diagnostic for active infection- antibodies develop days or weeks after infection

65
Q

Drugs used to treat covid (4)

A
  1. Remdesivir- antiviral, used for people older than 12 and who weigh more than 88 pounds. Blocks replication of multiple coronaviruses
  2. Dexamethasone corticosteroid that prevents death of those on oxygen or ventilators
  3. Baricitinib (EUA)- kinase inhibitor usually used to treat rheumatoid arthritis. Treats hospitalized adults that require oxygen/breathing assistance
  4. Monoclonal antibodies (EUA)- limited to non-omicron variants
66
Q

Covid prevention measures (7)

A
  1. COVID-19 vaccination
  2. Use a mask that covers the nose and mouth
  3. Maintain 1 meter distance from others
  4. Avoid crowds and poorly ventilated indoor spaces
  5. Wash and/or sanitize your hands frequently
  6. Cough/sneeze into your elbow
  7. Stay home if you’re sick, and don’t return until you are fever free for 24 hours without medications
67
Q

Who is covid vaccination recommended for?

A

The CDC recommends vaccination for everyone 5 years of age or older due to risk of complications with COVID-19

68
Q

4 types of covid vaccines

A
  1. Whole virus vaccine
  2. RNA or mRNA vaccine
  3. Non replicating viral vector (adenovirus)
  4. Protein subunit
69
Q

Which outcomes are covid vaccines effective against?

A

Highly effective against hospitalization and death, less effective against symptomatic infection (91% for Pfizer, 96% for moderna). Less effective in immunocompromised people

Microbiology (19 decks)

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