Microbiology Exam 4 Notes PDF

Microbiology Exam 4 How helpful is it to spend time reviewing the quiz questions? **Kinda**. Module19 - Antibiotics **Know the terminology associated with antimicrobials.** **Game made** **Magic Bullet**: chemical that could target a pathogen but not harm the host **Natural antibiotic**: compo...

Microbiology Exam 4 How helpful is it to spend time reviewing the quiz questions? **Kinda**. Module19 - Antibiotics **Know the terminology associated with antimicrobials.** **Game made** **Magic Bullet**: chemical that could target a pathogen but not harm the host **Natural antibiotic**: compounds made by a microorganism that kill or inhibit the growth of other microorganisms **Semisynthetic antimicrobials**: chemically modified antimicrobials **Spectrum**: which types of organisms are affected by antimicrobials **Narrow-spectrum antimicrobial**: will only affect a few specific types of bacteria **Broad-spectrum antimicrobial**: can affect many types of gram-positive and gram-negative bacteria **Superinfection**: 1. Normal microbiota keeps opportunistic pathogens in check. 2. Broad spectrum antibiotics kill nonresistant cells. 3. Drug resistant pathogens proliferate and can cause a superinfection. **Bacteriostatic**: inhibits the growth of an organism, but does not kill it **Bactericidal**: kills the target organism **Kirby-Bauer disk diffusion test**: utilizes diffusion on an agar plate from a liter disk containing the compounds and looks for zone of inhibition. The size of the sone is used to determine whether or not the organism is susceptible to the drug. **Zone of Inhibition**: a clear area around an antimicrobial agent where bacteria do not grow **Mueller-Hinton agar**: media used for Kirby-Bauer test **Selective-toxicity**: causes harm to the pathogen but not to the host **Be able to name scientists and describe their contribution to the history of antimicrobials.** **John Mueller & Jane Hinton**: developed Mueller-Hinton agar. Dr. Hinton was one of the first two African American women to earn a phd in veterinary medicine **Alexander Flemming**: father of antibiotics, discovered penicillin in 1928 **Dorothy Hodgkin**: analyzed the chemical structures of the natural products, allowing scientists to begin to chemically modify the molecule to create new semisynthetic antimicrobials, increasing the utility of the the original antimicrobial in the 1940's **Selman Waksman**: identified several antibiotics, including the first effective one against tuberculosis from *Streptomyces* in the 1950's **Paul Ehrlich**: looking for magic bullet **Know the major types of antimicrobials.** **Game made** Beta-lactams - cell wall Glycopeptides - cell wall Bacitracin - cell wall Fluoroquinolones - DNA synthesis Rifamycins - RNA synthesis Polymixins - plasma membrane Lipopeptide - plasma membrane 30S subunit - ribosomes 50S subunit - ribosomes Folic Acid Synthesis -metabolic pathways Mycolic Acid Synthesis - metabolic pathways **Be able to describe the different modes of actions used by antimicrobials to target microorganisms and match antibiotics to their mode of action based on the examples given in the course.** **Game made** **Plasma Membrane**: Disrupt the cell or outer membranes of the cell, which can lead to cell death. [Polymyxin]: polymyxin B & colistin [Lipopeptide]: daptomycin **Cell Wall Synthesis**: [Beta-lactams]: penicillins, cephalosporins, monobactams, carbapenems Beta-lactams inhibit the formation of peptide cross-links in peptidoglycan [Glycopeptides]: vancomycin Inhibit other steps related to peptidoglycan synthesis [Bacitracin] Inhibit other steps related to peptidoglycan synthesis **DNA Synthesis**: [Fluoroquinolones]: ciprofloxacin, levofloxacin & moxifloxacin Inhibit DNA gyros, which is important in the replication of bacterial chromosomes **RNA Synthesis:** [Rifamycins]: rifampin Inhibits bacterial RNA polymerases and prevents transcription **Ribosomes**: [30S subunit]: aminoglycosides & tetracyclines aminoglycosides: Targets 30S ribosome subunit and cause mismatches between codon and anticodon. This causes the translation of faulty proteins --- Protein synthesis tetracyclines: revent the tRNA from associating with the ribosome. [50S subunit]: macroslides, lincosamides, chloramphenicol, oxazolidinones Interact with 50S ribosomal subunit or prevent the initiation of protein synthesis **Metabolic pathways** [Folic Acid synthesis]: sulfomonamides, sulfones & trimethoprim sulfamethoxazole: broad spectrum - blocks the production of dihydrofolic acid, which is an important co-factor in metabolism, folic acid. [Mycolic acid synthesis]: izoniazid Narrow spectrum interferes with the synthesis of mycolic acids so it is effective against Mycobacterium specifically. **Be able to identify examples of antimicrobials against eukaryotic microorganisms.** **Do we need to know the groupings or specific drug?** Complicated because their cells have more similarities to ours, but each type of microorganism contains unique metabolic pathways or cell structures that can serve as antimicrobial targets. [Imizadoles (miconazole]): used to treat fungal skin infections and yeast infections [Quinolines (mefloquine]): antiprotozoan drugs used to treat malaria [Avermectins (ivermectin]): antihelminthic drug used to treat roundworm diseases like river blindness **Be able to discuss mechanisms of antibiotic resistance and factors contributing to this issue.** **OTHER FACTORS:** [Persister cells]: genetic characteristics that allow them to survive exposure to antibiotic [Superbug evolutions]: resistant to many different antibiotics [Horizontal gene transfer] (conjugation or transduction): genes for antibiotic resistance can bread horizontally among bacteria [Evolution]: Selective pressure changed the composition of the population in favor of those with resistance. Easier to kill will die first, leaving those harder to kill. [Long term concerns]: many antibiotics are already ineffective due to resistance Superbugs: only susceptible to a few antibiotics Not developing new antibiotics to replace those that are ineffective High cost to identify and test a new drug for humans. It's not profitable for companies, almost cyclical (new drug, misuse, resistant, start over) [Misuse of antibiotics]: helps select for bacteria already more resistant to the antibiotic Failing to complete the full course of prescribed antibiotic Using outdated or weakened antibiotics Using antibiotics for viral diseases Using antibiotics in animal feed **MECHANISMS**: [Efflux pump]: ejection of the antibiotic from the cell Fluoroquinolones Aminoglycosides Tetracyclines Beta-lactams Macrolides [Blocked penetration]: prevention of the drug from reaching the target site Beta-lactams Tetracyclines Fluoroquinolones [Target modification]: altering the target site of the drug Fluorqinolones Rifamycins Vancomycin Beta-lactams Macrolides Aminoglycosides [Inactivation of enzymes]: enzymatic destruction or inactivation of the drug Beta-lactams Aminoglycosides Macrolides Rifamycins   Module 20 **Be able to describe the concept of an emerging disease.** Disease that are new to human populations or that have seen a recent increase in cases Old disease that has come back due to come change in resistance, environment, etc **Be able to give examples of emerging diseases and be able to identify ways in which human impact on the environment influences emerging diseases.** [Current]: SARS, Zika, and Covid 19 [Older diseases] can become emerging diseases when numbers start to increase due to some change, like antibiotic resistance --- tuberculosis [Human impact]: deforestation and clearing of wildlands expose humans to new diseases might cause change in animal contact, stress to the animal causing more susceptibility to animal, Infrastructure like air conditioning and water piping can provide habitats for potential diseases Social conditions like poverty, homelessness or inadequate health care can make disease prevention more difficult Human travel greatly increases the spread of diseases beyond their point of origin   Module 21 **Define the different types of symbiosis.** [Mutualism]: Benefit - Benefit. Two species benefit each other. [Commensalism]: Benefit - Unaffected. [Amensalism:] Harmed - Unaffected. [Neutralism:] Unaffected - Unaffected [Parasitism:] Benefitted - Harmed [Antagonism:] Is this the same as amenalism? Not mentioned in this chapter of the book, but mentioned in the module A subset of amensalism. **Be able to provide an example of each type of symbiosis, including how each member benefits or loses from the interaction, using examples that include microorganisms.** [Mutualism]: humans and **some** strains of *E. Coli.* The bacterium relies on the intestinal contents for nutrients and humans derives certain vitamins from *E. coli,* particularly vitamin K [Commensalism]: Bacterium *Staphylococcus epidermidis* uses the dead cells of human skin as nutrients, but the human is not affected (as long as the immune system is healthy) [Amensalism:] *Staphylococcus epidermidis* is unharmed by the bacteriocin compounds it produces, but it can target and kill other potential pathogens [ this is better as antagonism.] [Neutralism]: coexistence of metabolically active (vegetating) bacteria and endospores (dormant metabolically passive bacteria), like *Bacillus anthracis* having both active and inactive cells in same soil. [Parasitism:] the relationship between human and many pathogenic prokaryotes because the organisms invade the body producing toxic substances or infectious diseases that cause harm. Humans and Tuberculosis. [Antagonism:] is this the same as amenalism? Not mentioned in this chapter of the book, but mentioned in the module **Do we need to know the 4 listed benefits of symbiosis? Yes. Big eye roll buddy.** Protection: living in association with a host or partner may provide protection against predation or environmental change Favorable position: as seen in lichens, the algal partner can remain in a position to receive sunlight and not be washed away Nutrition: availability of nutrients or growth factors may be increased Recognition: bioluminescent bacteria help certain fish in recognizing maters or for attracting prey  Module 22 **Be able to explain the characteristics of disease and know related terminology from Ch.15.** **Concentrate on what's mentioned in the modules? What is missing? Textbook. Virulence\*\* emias, exoenzymes, microtoxins, 15.1-15.3. Add fungal and helminths.** [Infection]: the organism has gotten into the host and started to colonize it. Invasion does not necessarily impact the health of the host. There can be infection but no disease. [Disease]: the change in the state of health of the infected host. Any condition in which the normal structure or functions of the body are damaged or impaired. [Signs of disease]: objective and measurable and can be directly observed by a clinician (vital signs - body temp, heart rate, breathing rate, blood pressure) [Symptoms]: are subjective - felt or experienced by the patient but they cannot be clinically confirmed or objectively measured (nausea, loss of appetite, pain, etc) Cyto-: cell Hepat-: of the liver -pathy: disease -emia: of the blood -itis: inflammation -lysis: destruction -oma: tumor -osis: diseased or abnormal condition -derma: of the skin [Asymptomatic or subclinical:] no noticeable signed or symptoms [Infectious disease]: caused by the direct effect of a pathogen. Can also be communicable or contagious [Communicable disease]: capable of being spread from person to person through direct or indirect mechanisms [Contagious disease]: spread from person to person, threat level being dependent on how the pathogen is transmitted [Noncommunicable disease]: not spread from one person to another Types of Noninfectious Diseases [Inherited]: a genetic disease [Congenital]: disease that is present at or before birth [Degenerative]: progressive, irreversible loss of function [Nutritional deficiency]: impaired body function due to lack of nutrients [Endocrine]: disease involving malfunction of glands that release hormones to regulate body functions [Neoplastic]: abnormal growth (benign or malignant) [Idiopathic]: disease for which the cause is unknown Periods of diseases [Incubation period]: initial entry of pathogen into the host, no signs or symptoms [Prodromal period]: pathogen multiplying and host begins to experience general signs and symptoms as a result of the immune system activating [Period of Illness]: signs and symptoms are the most severe and obvious [Period of decline]: number of pathogens begin to decrease and signs/symptoms begin to decline. Host may be susceptible to secondary infection at this time bc they're already compromised [Period of convalescence]: host returns to normal functions, although some diseases may inflict permanent damage Diseases based on [Prevalence] [Sporadic]: irregular intervals [Endemic]: found at a low or expected frequency and at a fairly regular interval [Epidemic]: larger than normal number of cases of a certain disease in a short amount of time [Pandemic]: epidemic that spreads beyond a region and becomes widespread in many countries or continents [Reservoirs are a source of disease] [Humans] [Animals] - [zoonotic disease] if spread from an animal to a human [Nonliving]: environmental factors (water, soil or surfaces like doorknobs). Surfaces and objects that can be sources of disease are also known as [fomites]. Classification by [severity or duration] [Acute]: infected person gets sick quickly, the disease peaks and then the patient either gets better or succumbs to the disease [Latent]: may have initial acute phase, but then become dormant with no symptoms, then reactivate at a later date. [Chronic]: typically develop slowly and can be continual or with recurrent severity [Host involvement] [Localized infections:] local or limited area of the body [Generalized or systemic infection]: if the infection spreads throughout the body [Bacteremia]: presence of bacteria in the blood [Septicemia]: bacteria growing and dividing in the blood how to differential between bacteremia and septicemia? Division is the key. [Toxemia]: bacterial toxins or other toxins in the blood [Viremia]: viruses in the blood Routes of [entry] [Respiratory] [Gastrointestinal] [Sexually transmitted] [Parenteral (cuts or breaks in the skin)] Other Infection terminology [Primary infection]: when a healthy person first becomes infected. In some cases, they may now be more susceptible to other infections [Secondary infection]: an infection that enters a susceptible individual [Focal infection]: localized pathogen [Systemic infection]: an infection disseminated throughout the body [Opportunistic infection]: a pathogen that wouldn't normally be able to cause disease in a healthy person, but can do so in a weakened host [Nosocomial infection]: a secondary infection acquired while patients are in hospitals Iatrogenic diseases: contracted as a result of a medical procedure [Pathogenicity]: the ability of a microbial agent to cause disease [Virulence]: the degree to which an organism is pathogenic [Stages of pathogenesis]: must be able to gain entry to the host, travel to where it can establish an infection, overcome the host's immune response, and cause damage. Cycle usually ends when the pathogen exits the host and is transmitted to a new host Exposure (contact) Adhesion (colonization) Invasion Infection [Viral adhesins]: part of the viral capsid or membrane envelope Antigenic drift: the result of point mutations causing slight changes in the spike proteins hemagglutinin and neuraminidase Antigenic shift: a major change in spike proteins due to gene reassortment [Toxins]: biological poisons that assist in pathogens ability to invade and cause damage to tissue [Toxigenicity]: the ability of a pathogen to produce toxins [Endotoxins]: LPS found on the outer membrane of a gram-negative bacteria [Exotoxin]: protein molecules that are produces bye a wide variety of living pathogenic bacteria [Hemolysins]: membrane disrupting exotoxin that causes pores to form in cell membranes causing cell cytoplasm leakage and cell lysis [Superantigens]: exotoxins that trigger an excessive, nonspecific stimulation of immune cells to secrete cytokines [Exoenzymes]: extracellular enzymes produced by pathogens that enable them to invade host cells and deeper tissues Glycohydrolases: degrades hyaluronic acid that cements cells together to promote spreading through tissues Nucleases: degrades DNA release by dying cells (bacteria and host cells) that can trap the bacteria, thus promoting spread Phospholipases: degrades phospholipid bilayer of host cells, causing cellular lysis and degrade membrane of phagosomes to enable escape into the cytoplasm Proteases: degrades collagen in connective tissues to promote spread [TORCH Infections]: pathogens capable of crossing the placental barrier Portals of Entry Eye Nose Mouth Ear Placenta (for fetus) Vagina Urethra Anus Broken skin Insect bite Needle [Fungal virulence]: adhesins, exoenzymes, capsule production, [Protozoan virulence]: adhesins, toxins, antigenic variation, ability to survive inside phagocytic vesicles, unique attaching features, [Helminth virulence]: proteases to penetrate skin, large size, tough outer cuticle, changing surfaces during life cycles, active suppression of immune system [Mycotoxins]: fungal toxins [Carcinogen]: a substance involved in causing cancer **Be able to describe Koch's Postulates.** The same pathogen must be present in every case of the disease The pathogen must be isolated from the diseased host and grown in pure culture The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal The pathogen must be isolated from the inoculated animal and must be shown to be the original organism \*\*\*a modification to these for diseases where we cannot culture the pathogen. Scientists will use molecular methods to identify the cause. **Be able to describe the different portals of entry for pathogens.** [Respiratory] [Gastrointestinal] [Sexually transmitted] [Parenteral (cuts or breaks in the skin)] **Know the difference between nonspecific/innate and adaptive immunity and an example of each.** [Innate]: present at birth, nonspecific and blocks all types of infection. [Skin ] [saliva & tears] (enzymes that can destroy pathogens before they can infect) [immune system] (all foreign bodies targeted for destruction) [Adaptive]: developed over time as the immune system is exposed to different antigens & recognizes specific pathogens to target them [B & T cells]: recognize antigens (portions of foreign bodies) and produce antibodies to bind to the antigen [Vaccines]: expose a person to the antigen allowing the immune system to react and produce antibodies. Can be [subunit vaccines] (a portion of the pathogen) or [attenuated] (a weakened form of the pathogen)   **For diseases of each type of microorganism (bacteria, viruses, prions, protozoa, algae, fungi, and helminths), be able to:** Identify diseases associated with this type of microorganism, including major symptoms, causative agent (genus). \[After conclusion of Module 23, a list of organisms will be posted. You are responsible for knowing the major characteristics and causative organism name for the diseases on this list for the exam.\] Just needs genus, virus just names not genus usually **Bacterial:** **Tuberculosis** Symptoms: cough with phlegm or blood, chest pain, weight loss Causative Agent: *Mycobacterium tuberculosis* **Streptococcal pharyngitis** Symptoms: throat pain, swollen lymph nodes, fever Causative Agent: *Streptococcus pyogenes* **Tetanus** Symptoms: muscle spasms, stiffness, difficulty swallowing Causative Agent: *Clostridium tetani* **Cholera** Symptoms: diarrhea, vomiting, dehydration Causative Agent: *Vibrio cholerae* **Lyme disease ** Symptoms: red circular rash, fever, chills Causative Agent: *Borrelia burgdorferi* **Chlamydia** Symptoms: pain or burning while peeing, pain during sex, abnormal discharge Causative Agent: *Chlamydia tracomatis* ** ** **Viral:** **Influenza** Symptoms: fever, muscle ache, chills and sweats Causative Agent: *Orthomyxovirus* **AIDS** Symptoms: weight loss, fever, fatigue Causative Agent: Human Immunodeficiency Virus **COVID-19** Symptoms: fever or chills, cough, shortness of breath Causative Agent: SARS-CoV-2 **Measles** Symptoms: fever, cough, rash and Koplik spots Causative Agent: Morbillivirus **Chicken pox** Symptoms: rash, fever, fatigue Causative Agent: Varicella-Zoster virus **Ebola** Symptoms: early (fever, muscle pain, fatigue), later (unexplained bleeding, gastrointestinal symptoms, nausea) Causative Agent: Orthoebolaviruses ** ** **Prion: do we need to name things more specifically than prion? Hard time finding that** **Creutzfeldt-Jakob** Symptoms: dementia, movement abnormalities, cognitive impairment Causative Agent: prion **Mad Cow Disease** Symptoms: difficulty walking & getting up, nervousness or violence, weight loss Causative Agent: prion **Kuru** Symptoms: abnormal involuntary movements, body stiffness, sudden mood changes Causative Agent: prions ** ** **Protozoal:** **Malaria** Symptoms: shivering, fever, chills Causative Agent: *Plasmodium falciparum* **Giardiasis** Symptoms: diarrhea, gas and bloating, stomach cramps Causative Agent: *Giardia duodenalis* **Toxoplasmosis** Symptoms: flu-like symptoms, eye symptoms, slurred speech Causative Agent: *Toxoplasma gondii* **Amoebiasis** Symptoms: diarrhea, stomach pain, weight loss Causative Agent: *Entamoeba histolytica* **African trypanosomiasis** Symptoms: early (fever, headache, joint pain), later (sleep disturbances, confusion, poor coordination) Causative Agent: *Trypanosoma brucei* ** ** **Algal:** **Ciguatera** Symptoms: vomiting, tingling, headache Causative Agent: *Gambierdiscus toxicus* **Protothecosis** Symptoms: diarrhea, weight loss, inflammation of the eye Causative Agent: *Prototheca* **Paralytic Shellfish Poisoning** Symptoms: tingling, nausea, vomiting Causative Agent: *Gymnodinium* **Amnesic Shellfish Poisoning** Symptoms: nausea, confusion, memory loss Causative Agent: *Pseudo-nitzschia* ** ** **Fungal:** **Ringworm** Symptoms: ring shaped rash, itchy, brittle hair Causative Agent: *Trichophyton* **Candidiasis** Symptoms: rash, soreness, itching Causative Agent: *Candida* **Histoplasmosis** Symptoms: fever, cough, fatigue Causative Agent: *Histoplasma capsulatum* **Aspergillosis** Symptoms: coughing up blood or mucus, shortness of breath, chest pain Causative Agent: *Aspergillus* ** ** **Helminthic:** **Ascariasis** Symptoms: blocked intestines, abdominal cramping and vomiting Causative Agent: *Ascaris lubricoides* **Schistosomiasis** Symptoms: high temperature, fever, cough Causative Agent: *Schistosoma* **Hookworm** Symptoms: abdominal pain, diarrhea, fatigue Causative Agent: *Nector americanus* **Enterobiasis** Symptoms: itchiness around anus, sleep disturbances, irritability Causative Agent: *Enterobius vermicularis* **Filariasis** Symptoms: swelling, skin changes, coughing Causative Agent: *Wuchereria bancrofti*   Module 24 For disease that affect each body system, be able to: Know the difference between a food infection like Salmonella food poisoning and a food intoxication like Staphylococcus food poisoning. [Food infection]: organism is ingested, invades the intestinal lining and multiplies [Food intoxication]: an organism produces a toxin in food, which is then ingested Identify a disease for each body system, name the causative agent (genus or virus name), and major features of the disease. \[When possible, it is suggested that you use diseases from the list in Module 23 to answer the questions in Module 24 to minimize the number of different diseases you need to remember\] a\. Name an antibiotic-resistant strain of bacteria that causes disease of the **skin**: Methicillin-resistant Staphylococcus aureus (MRSA) MRSA can cause intense skin infections, like boils, and can be potentially life-threatening. b\. What is **inflammation of the tissues surrounding the eye** called? Uveitis Uveitis can cause the eye to be red, swollen, and itchy, and can potentially lead to permanent vision loss. c\. The disease known as "**ringworm**" is actually caused by what type of organism? What scientific term is used for these skin infections? Fungus Tinae Infections Ringworm is spread by skin-to-skin contact and causes scaly, itchy patches, usually in a bullseye pattern. d\. What disease of the **respiratory system includes the formation of a pseudomembrane in the throat**? Diphtheria Diphtheria is spread through respiratory droplets or saliva, and impacts the respiratory system. e\. What type of pneumonia is caused by ***Mycoplasma pneumonia***? Walking pneumonia Walking pneumonia can present very similarly to the common cold and can be diagnosed with a chest X-ray to see if there is mucus in the lungs. f\. **Rhinoviruses** are a typical cause of what type of respiratory disease? Common cold Rhinoviruses can be contagious for up to two weeks and you can spread the virus up to two days before symptoms appear. g\. Name a disease caused by a **spirochaete that is sexually transmitted**: Syphilis There are three major stages to this disease, starting with a painless sore, moving into a rash, and then much later, damage to the nervous system, heart and eyes. h\. Name a disease that is a **food-borne infection**: Listeriosis Listeriosis can be extra dangerous for pregnant persons, resulting in the loss of the baby or serious infection of the baby. i\. Name a disease that is a **food intoxication**: Botulism Low-acid foods are the most risky for this diseased the most common in homemade food, like canning, fermenting and preserving. j\. **Noroviruses** are associated with what type of disease? Gastroenteritis Gastroenteritis is most commonly known as the stomach flu and only lasts for a couple of days. k\. What **intestinal disease is caused by a flagellated protozoan** and associated with contaminated water? Giardiasis The most common symptom of Giardiasis is diarrhea and fatigue. l\. This **roundworm** infects almost 1 billion people worldwide and can cause intestinal blockages. *Ascaris lumbricoides* Symptoms associated with *Ascaris lumbricoides* include digestive issues, respiratory issues, low-grade fever, rash and loss of appetite. m\. This **tapeworm** genus is associated with intestinal infections from undercooked meat. *Taenia* The spread of this tapeworm can be prevented by cooking pork to an internal temperature of 145\*F. n\. Name a **bacterial toxemia** that primarily affects the circulatory system and can cause individuals to go into shock: Toxic Shock Syndrome Toxic Shock Syndrome can be caused by leaving a tampon in for too long. o\. Name a **mosquito-borne viral disease of the circulatory system** that results in jaundice. Yellow Fever Jaundice is a severe symptom of Yellow Fever and gives the disease its name, as the skin turns yellow. p\. Name a **protozoal disease of the blood that is spread by mosquitos** and the genus of the protozoan. Malaria *Plasmodium* More than 600,000 people die of malaria each year. q\. What is an infection of the **tissues around the brain called**? Name a bacterial genus that can cause this type of infection. Meningitis *Neisseria* Meningitis is most common in children and young people, but can impact a person of any age. r\. Name a **viral disease that affects the nervous system and can cause microcephaly** in a fetus if contracted during pregnancy. Zika virus Zika virus can be transmitted through the bite of an infected mosquito, sexual contact, mother to fetus, blood transfusions or organ transplants.