viral infections Flashcards
1
Q
viruses
A
- acellular pathogens that invade living cells (can’t survive without a host)
- either kill host cell or alter its functions
- composed of nucleic acid (DNA or RNA) surrounded by protein coat
- viruses are microscopic agents visible only with an electron microscope
- lack enzymes for energy production & protein synthesis
- cannot grow or reproduce independently & need a host cell to replicate
2
Q
parasites
A
- organisms that live on or in a living host; relationship benefits the parasite & harms the host
3
Q
mechanism of viral infection
A
- viruses invade host cells & shed their protein coats
- genetic material of the virus takes control of the host cell, directing it to produce more viruses
- immune system fights viruses by producing substances such as interferon, which also cause symptoms of viral illnesses
4
Q
contagious diseases
A
- viral diseases are the most common forms of contagious diseases
- contagious diseases can be transmitted from one person to another, often through respiratory droplets or hand-to-hand contact
- examples; common cold & influenza
5
Q
common cold
A
- caused by over 200 different viruses, including rhinoviruses & coronaviruses
- transmission primarily through hand-to-hand contact
- prevention; frequent hand washing & avoiding touching the face after contact with others
- symptoms; sore throat, runny nose, muscle aches, thick nasal discharge
- OTC remedies can alleviate symptoms but do not cure viral infection
- not caused by exposure to cold weather or being chilled, but more colds occur in fall and winter due to closer indoor contact
6
Q
influenza (flu)
A
- serious respiratory tract infection caused by influenza virus
- highly infectious & adaptable; form changes so easily that every year new strains arise, making treatment difficult
- symptoms; fever, extreme fatigue, headache, cough, muscle aches
- spread via respiratory droplets
- prevention; annual vaccination with vaccine updated each year to match circulating strains
- treatment; medications can shorten the duration of illness if taken within one to two days of symptom onset
- complications; can include pneumonia & other life-threatening conditions
- highest infection rates are in children
- compared with the common cold, influenza is more serious
7
Q
measles & rubella
A
- characterized by rash & fever
- can cause severe complications like liver or brain infection or pneumonia
- highly contagious
- effective vaccination has significantly reduced cases
- rubella (German measles);
- mild illness but can cause severe birth defects if a pregnant woman is infected
- vaccination has reduced incidence
8
Q
mumps
A
- causes swelling of the salivary glands
- an lead to meningitis and, in males, inflammation of the testes
- cases have decreased due to vaccination
9
Q
chickenpox, coldsores, & herpesvirus infections
A
- herpesviruses = large group of viruses that remain latent in body & can reactivate periodically
- once infected, host is never free of the virus
- virus lies latent within certain cells & becomes active periodically, producing symptoms
- responsible for cold sores, mononucleosis, chicken pox, & STI herpes; frequently cause
latent infections
10
Q
varicella-zoster virus
A
- included in herpesviruses
- causes chicken pox & shingles
- highly contagious childhood disease characterized by itchy rash made up of small blisters
- complications more likely to occur in young infants & adults
11
Q
epstein-barr virus (EBV), aka mono
A
- included in herpesviruses
- causes infectious mononucleosis
- spread by intimate contact with saliva of infected person
- fever, sore throat, swollen lymph nodes, & fatigue
12
Q
cytomegalovirus (CMV) & human herpesvirus 8 (HHV-8)
A
- included in herpesviruses
- can cause severe infections in immunocompromised individuals
- CMV injects lungs, brain, colon, & eyes
- HHV-8linked to Kaposi’s sarcoma
13
Q
viral encephalitis
A
- inflammation of brain tissue caused by viral infection
- causes; HSV-1, HIV, mosquito-borne viruses
- symptoms; fever, headache, nausea, lethargy, memory loss, seizures, possible permanent brain damage or death
14
Q
viral hepatitis
A
- used to describe several different infections that cause inflammation of liver
- hepatitis is usually caused by one of the three most common hepatitis viruses;
- effective vaccines for hep A & B but new cases occur each year
- symptoms; fatigue, jaundice, abdominal pain, loss of appetite, nausea, diarrhea
15
Q
hepatitis A virus (HAV)
A
- mild, transmitted by contaminated food or water
16
Q
hepatitis B virus (HBV)
A
- transmitted sexually
17
Q
hepatitis C virus (HCV)
A
- transmitted through blood, common among injection drug users
- chronic carriers; 5-10% of HBV infections & 85-90% of HCV infections become chronic
- chronic carriers can infect others & may develop liver disease, cirrhosis, or liver cancer (some remain asymptomatic)
- jaundice = characterized by yellowing of the skin and eyes due to increased bile pigment levels in the blood
18
Q
poliomyelitis (Polio)
A
- infectious viral disease affecting nervous system
- can cause irreversible paralysis & death in some individuals
- dramatic decline in incidence in Canada post-vaccine introduction
- North & South America now considered polio-free
19
Q
rabies
A
- infectious viral disease caused by rhabdovirus, potentially fatal infection of central nervous system
- transmission typically occurs through an animal bite
- significant decline in human rabies-related deaths in Canada due to vaccination of domestic animals & development of post-exposure prophylaxis (PEP)
- rare in Canada, with only 24 deaths since 1924
- most recent cases traced to bats
- PEP recommended for anyone with direct or possible indirect contact with a bat
- PEP involves one dose of immunoglobulin and five doses of rabies vaccine over 28 days
20
Q
human papillomavirus (HPV)
A
- consists of more than 100 different types causing various warts, including common, plantar, & genital warts
- chronic infection can lead to recurring warts despite treatment
- major cause of cervical cancer
- treatments include OTC preparations & professional methods (laser surgery or cryosurgery)
- 2 vaccines approved by Health Canada;
- one for females aged 9 to 45 & males aged 9 to 26
- second vaccine for females aged 9 to 26
21
Q
treating viral illnesses
A
- antiviral drugs interfere with the viral life cycle, preventing entry into cells or reproduction within cells
- available for HIV, influenza, herpes simplex, varicella-zoster, HBV, & HCV
- most viral diseases must run their course without specific treatment
22
Q
fungi
A
- absorb food from organic matter & can be multicellular (moulds) or unicellular (yeasts)
- common fungi include mushrooms & moulds on bread & cheese
- only about 50 species cause human diseases, typically affecting skin, mucous membranes, & lungs
23
Q
fungi diseases
A
- Candida albicans; common in vagina; overgrowth causes yeast infections
- factors include antibiotics, warm/moist clothing, pregnancy, oral contraceptives, & certain diseases.
- symptoms; thick white or yellowish discharge
- treatment; prescription and OTC available (self-treatment not recommended)
- other conditions; athlete’s foot, jock itch, ringworm (mild and treatable)
- systemic fungal diseases; severe, life-threatening, hard to treat
- ex; histoplasmosis (common in Mississippi & Ohio River Valleys), coccidioidomycosis (California)
24
Q
protozoa
A
- single-celled organisms, causing recurrent, cyclical disease attacks
- release enzymes or toxins that destroy cells
- millions affected by protozoa diseases in developing countries
25
common protozoa diseases
- malaria; caused by plasmodium, transmitted via mosquito bite
- severe flu-like symptoms, may cause anemia
- prevention & treatment drugs available (distribution challenging in remote areas)
- giardiasis; caused by Giardia lamblia
- nausea, diarrhea, bloating, abdominal cramps
- transmission; contaminated food/water, surfaces
- common in child care settings, travellers, hikers
- rarely serious, treatable with medication
26
other protozoal infections
- trichomoniasis; vaginal infection, may increase HIV risk
- trypanosomiasis; African sleeping sickness, transmitted by tsetse fly, causes severe symptoms and death
- amoebic dysentery; caused by Entamoeba histolytica, results in bloody diarrhea, stomach pain, fever
27
parasitic worms
- largest infectious organisms, causing variety of mild infections
- attack tissues or organs & compete with host for nutrients
- some enter by burrowing through skin, others via undercooked pork or fish
- adult worms can be meters long
28
common parasitic diseases
- tapeworms, hookworms, pinworms, flukes
- pinworms; common in children, cause rectal itching, sleep difficulties
- flukes; infect liver/lungs, potentially deadly
- infections usually stem from contaminated food or drink, controllable by hygiene
29
prions
- proteinaceous infectious particles causing fatal central nervous system disorders
- lack DNA/RNA, consist only of protein, do not trigger immune response
- abnormal shape, form brain deposits
- spongiform encephalopathies (TSEs), including Creutzfeldt-Jakob disease (CJD) & bovine spongiform encephalopathy (BSE, or mad cow disease)
- symptoms; loss of coordination, weakness, dementia, death
- transmission; inherited, genetic mutations, infected tissue consumption, medical procedures
30
zika virus
- emerging infectious disease
- transmission; Aedes mosquitoes, sexual contact, mother to fetus
- symptoms; mild (fever, rash, joint pain), potential for Guillain-Barré syndrome
- pregnancy concerns; birth defects (microcephaly, growth impairment, eye defects)
31
west nile virus
- emerging infectious disease
- transmission; mosquitoes from infected birds
- symptoms; mild or none, potential brain damage or death
- vaccine development ongoing
32
SARS
- emerging infectious disease
- transmission; originally from wildlife, spread rapidly
- symptoms; pneumonia, fatal in 4% of cases
- outbreak; controlled since 2004
33
rotavirus
- emerging infectious disease
- transmission; poor hygiene/sanitation
- symptoms; gastroenteritis in children, severe diarrhea
34
E. coli O157:H7
- emerging infectious disease
- transmission; contaminated food/water
- symptoms; bloody diarrhea, kidney damage
35
hantavirus
- emerging infectious disease
- ransmission; rodent droppings/urine
- symptoms; pulmonary syndrome, high fatality rate
36
ebola
- emerging infectious disease
- transmission; contact with infected bodily fluids
- symptoms; hemorrhagic fever, high fatality
- outbreaks; primarily in Africa, 2014 outbreak largest recorded
37
other immune disorders
- cancer; immune system detects & destroys cancerous cells
- breakdown in immune response allows cancer to proliferate
- autoimmune diseases; immune system mistakenly attacks body's own cells
- common autoimmune diseases: rheumatoid arthritis, systemic lupus erythematosus
- autoimmune disorders more common in women
38
factors contributing to emerging infections pt1
- drug resistance = increasing resistance in malaria, tuberculosis, gonorrhea, influenza, AIDS, pneumococcal, & staphylococcal infections
- consequence; prolonged illness, higher mortality, more expensive treatments
- poverty = over 1 billion in extreme poverty, lack access to essential drugs
- urbanization, overcrowding, migration spread diseases
- public health breakdown = poor infrastructure, contaminated water, inadequate vaccination
- natural disasters disrupt public health systems
- travel & commerce = increased global travel and trade spread infectious agents
- notable examples: SARS, cholera reintroduction, Zika spread
39
factors contributing to emerging infections pt2
- mass food production & distribution = long-distance food travel increases contamination risk
- chance contamination can lead to widespread illness
- human behaviours = injectable drug use spreads HIV/hepatitis
- changes in sexual behaviour increase STIs
- daycare use increases certain infections
- bioterrorism = deliberate release of infectious agents like anthrax, smallpox, plague, botulism, and viral hemorrhagic fevers
- high concern for public health
- climate change = longer warm periods, milder winters allow pathogenic species to expand range
- insects, vectors more active in previously unaffected regions
