MICROBIOLOGY REPORT ALL ABOUT INFO OF VIRUSES

About viruses

1. VIRUS Reporter: Rochelle M. Fandivila Bio 3B

2. Objectives: At the end of discussion students will be able to learn the following: Characteristics of Viruses How do viruses work? Types of Viruses Diseases caused by Virus

3. Virus Viruses are microscopic organisms that can infect hosts, like humans, plants or animals. They’re a small piece of genetic information (DNA or RNA) inside of a protective shell (capsid). Some viruses also have an envelope . Viruses can’t reproduce without a host. Some common diseases caused by viruses include the flu, the common cold and COVID-19.

4. ANATOMY What are the characteristics of viruses?

5. Virus shapes Viruses can look very different from each other. Scientists often described them by shape. Types of virus shapes include : Icosahedral or polyhedral- t his is a geometric shape with many sides, similar to a soccer ball. Most viruses that infect people are icosahedral. Examples:   poliovirus , rhinovirus, and adenovirus

6. Helical - t his virus shape looks like a cylinder. Its genetic information is coiled up like a spring inside . Examples: influenza virus, measles virus, mumps virus, rabies virus, and Ebola virus. Spherical - spherical viruses are helical or polyhedral viruses that have an envelope around them. They’re shaped mostly like a ball. Examples: Human Immunodeficiency Virus (HIV), herpes virus, poliovirus, and coronavirus.

7. Complex . Complex viruses combine more than one shape. Viruses that infect bacteria have a polyhedral “head” connected to a helix “body.” Examples: Poxviruses, geminiviruses , and many bacteriophages.

8. Virus size All viruses are very small — too small to see without a strong microscope. If you measure them under a microscope, most are between 20nm (nanometers) to 400nm. For comparison, the smallest viruses are about 2,000 times smaller than a grain of sand. They’re about 100 to 1,000 times smaller than the cells in your body. But their sizes can vary a lot. For instance, the measles virus is about five times larger than Zika virus. Viruses also have varying weights (molecular weight).

9. Genomic properties of viruses Viral DNA or RNA can be : Linear or circular. Positive-sense or negative-sense- RNA that’s positive-sense can be used as instructions to make more virus parts without any additional steps. Negative-sense RNA viruses need special proteins (enzymes) to create positive-sense RNA before viruses can make more copies of themselves. This is also called “plus-strand” (or “positive-strand”) or “minus-sense” (or “negative-strand”). Most DNA viruses are positive-sense. Single-stranded or double-stranded-  DNA viruses can have their genetic material in a single string of instructions ( ssDNA ), or two sets that are paired together (dsDNA). (Human DNA is double-stranded.) RNA viruses are usually single-stranded, though there are some double-stranded RNA viruses.

10. Structural proteins The structural proteins of a virus make up the capsid, or protective coating. They can also make up the envelope, if there is one, and any structures that stick out from it that help it enter cells (like the spike proteins of coronaviruses ). Example: SARS-CoV-2 It has four structural proteins, S (spike), E (envelope), M (membrane), and N ( nucleocapsid ) proteins; the N protein holds the single strand , positive-sense RNA genome, and the S, E, and M proteins together create the viral envelope. 

11. Virus features Viruses share some common features. Viruses: Are made up of  genetic material  (RNA or DNA) and a protective protein coating (capsid). Sometimes have another layer called an envelope around the capsid. Viruses without an envelope are called “naked viruses.” Are similar to parasites — they need a host to reproduce. They’ll survive outside of a host until their capsid breaks down over time. Are 100 to 1,000 times smaller than the cells in your body.

12. FUNCTION How do viruses get into your body?

13. Viruses usually enter your body through your  mucous membranes . These include your eyes, nose, mouth, penis, vagina and anus. Some viruses get in through a break in your skin or from a bite from a mosquito or tick . Viruses have several steps to infecting cells and reproducing. They include: Attachment. Entry. Replication Assembly. Release.

14. Attachment and entry Viruses can get inside of cells in three ways: Receptor binding- cells have receptors on the outside that can receive signals from proteins in your body. Direct fusion- some viruses attach directly to host cells to get inside. Bacteriophages inject their genetic material into bacterial cells. The entire virus doesn’t need to get inside.

15. Replication, assembly and release Once the virus or its genetic material is inside of a cell, it uses either a lytic cycle or lysogenic cycle to reproduce (some use both): Lytic cycle- t he virus uses the host cell’s machinery to make more copies of itself. Pieces of the virus assemble, wrapping up the genetic material in the capsid. Viruses make many copies of themselves this way.

16. Lysogenic cycle- s ome viruses have a dormant, or silent phase. They get inside cells and then wait. Each new copy of the cell also has a copy of the virus in it. Certain triggers can cause those cells to burst, spreading viral particles into your body that can infect other cells. Triggers could include stress, chemical signals or temperature changes.

17. TYPES OF VIRUSES

18. What are the types of viruses? Experts group viruses into categories — like family and genus — based on similar features, like size, shape and the type of genetic material they carry. Some common types of viruses that you might hear about include : Influenza viruses. Human herpesviruses. Coronavirus. Human papillomaviruses. Enteroviruses. Flaviviruses . Orthopoxviruses . Hepatitis viruses. There are also some viruses that have unique qualities, like retroviruses and oncoviruses .

19. Influenza viruses ( Orthomyxoviridae ) The  Orthomyxoviridae  family of viruses includes influenza A and B, which cause  the flu . Strains of influenza A also cause  avian flu (“bird flu”)  and  swine flu (H1N1). Human herpesvirus ( Herpesviridae ) Herpesviridae  is a large family of viruses. They cause several types of illnesses, like oral and genital herpes,  chickenpox ,  shingles ,  Epstein-Barr  and  cytomegalovirus (CMV ). Coronaviruses Coronaviruses are a subfamily of viruses. SARS-CoV-2, the virus that causes  COVID-19 , is probably the most well-known coronavirus. But other types of coronaviruses cause mild illnesses, like a cold. Human papillomavirus (HPV) Human papillomaviruses  are part of the  Papillomaviridae  family of viruses. They cause warts. Some types of HPV can lead to cancers.

20. Enteroviruses Enterovirus  is a genus (one level smaller than the group called a “family”) of viruses that infect your intestinal tract. Types of enteroviruses cause  polio  and  hand, foot and mouth disease. Flaviviruses Viruses in this genus are often spread by mosquitoes. They cause illnesses like  Zika ,  West Nile,   dengue fever  and  yellow fever. Orthopoxviruses Viruses in the genus  Orthopoxvirus  cause blistering rashes.  Mpox  and  smallpox  are orthopoxviruses . Hepatitis viruses Though they don’t all belong to the same family or genus, hepatitis viruses all infect your liver.  Hepatitis A , B and C are the most common.

21. Retroviruses Retroviruses are RNA viruses that use special proteins to make DNA. The virus then inserts its DNA into yours. Your cells read the viral DNA as if it were its own instructions.  HIV  and human T- lymphotropic virus 1 (HTLV-1) are retroviruses. Oncoviruses Oncoviruses are viruses that can cause cancer. Viruses that have been linked to specific cancers include: HPV. Epstein-Barr. HIV. Hepatitis B  and C. HTLV-1. Human herpesvirus 8 (HHV-8).

22. Conditions and Disorders What are some diseases caused by viruses?

23. Viruses can cause respiratory illnesses, “stomach flus,” sexually transmitted infections (STIs), skin conditions and many other kinds of illnesses. Some commonly known viral infections include : Common colds . The flu (influenza). COVID-19. Respiratory syncytial virus (RSV). Chickenpox. Measles. HIV/AIDS. HPV/genital warts. Genital herpes (HSV) . Polio . Rabies. Mpox . Zika . Hepatitis.

24. Are viruses living or nonliving?

25. Viruses aren’t living organisms . But there’s some debate over this. Generally, biologists don’t consider viruses to be alive because they can’t perform the functions that living organisms do. For instance, they can’t convert food into energy ( metabolism ) and they can’t live or reproduce without a host cell. On the other hand, they can reproduce in the right host cell and they evolve over time to survive. Plus, they can damage and destroy host cells to do so. Because of this, many consider them a “gray area” between living and nonliving things.

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