Antiviral drugs are a class of medication used for treating viral infections rather than bacterial ones. Most antivirals are used for specific viral infections, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do not destroy their target pathogen. Antiviral drugs are one class of antimicrobials, a larger group which includes antibiotic and antiparasitic drugs, or antiviral drugs based on monoclonal antibodies. Most antivirals are considered harmless to the host, therefore can be used to treat infections, they should be distinguished from viricides, which are not medication but deactivate or destroy virus particles, either inside or outside the body. Natural antivirals are produced by some plants such as eucalyptus and Australian tea trees. Most of the antiviral drugs now available are designed to help deal with HIV, herpes viruses, the hepatitis B and C viruses, influenza A and B viruses. Researchers are working to extend the range of antivirals to other families of pathogens.

Designing safe and effective antiviral drugs is difficult, because viruses use the host's cells to replicate. This makes it difficult to find targets for the drug that would interfere with the virus without harming the host organism's cells. Moreover, the major difficulty in developing vaccines and anti-viral drugs is due to viral variation; the emergence of antivirals is the product of a expanded knowledge of the genetic and molecular function of organisms, allowing biomedical researchers to understand the structure and function of viruses, major advances in the techniques for finding new drugs, the pressure placed on the medical profession to deal with the human immunodeficiency virus, the cause of acquired immunodeficiency syndrome. The first experimental antivirals were developed in the 1960s to deal with herpes viruses, were found using traditional trial-and-error drug discovery methods. Researchers infected them with the target virus, they introduced into the cultures chemicals which they thought might inhibit viral activity, observed whether the level of virus in the cultures rose or fell.

Chemicals that seemed to have an effect were selected for closer study. This was a time-consuming, hit-or-miss procedure, in the absence of a good knowledge of how the target virus worked, it was not efficient in discovering effective antivirals which had few side effects. Only in the 1980s, when the full genetic sequences of viruses began to be unraveled, did researchers begin to learn how viruses worked in detail, what chemicals were needed to thwart their reproductive cycle. Viruses consist of a genome and sometimes a few enzymes stored in a capsule made of protein, sometimes covered with a lipid layer. Viruses cannot reproduce on their own, instead propagate by subjugating a host cell to produce copies of themselves, thus producing the next generation. Researchers working on such "rational drug design" strategies for developing antivirals have tried to attack viruses at every stage of their life cycles; some species of mushrooms have been found to contain multiple antiviral chemicals with similar synergistic effects.

Compounds Isolated from fruiting bodies and filtrates of various mushrooms have broad spectrum antiviral activities, but successful production and availability of such compounds as frontline antiviral is a long way away. Viral life cycles vary in their precise details depending on the type of virus, but they all share a general pattern: Attachment to a host cell. Release of viral genes and enzymes into the host cell. Replication of viral components using host-cell machinery. Assembly of viral components into complete viral particles. Release of viral particles to infect new host cells. Several factors including cost, vaccination stigma, acquired resistance limit the effectiveness of antiviral therapies; these issues are explored via a health policy perspective. Cost is an important factor that limits access to antivirals therapies in the United States and internationally; the recommended treatment regimen for hepatitis C virus infection, for example, includes sofosbuvir-velpatasvir and ledipasvir-sofosbuvir.

A twelve-week supply of these drugs amount to $113,400 and $89,712, respectively. These drugs can be manufactured generically at a cost of $100 - $250 per 12 week treatment. Pharmaceutical companies attribute the majority of these costs to development expenses. However, critics point to monopolistic market conditions that allow manufacturers to increase prices without facing a reduction in sales, leading to higher profits at patient's expense. Intellectual property laws, anti-importation policies, the slow pace of FDA review limit alternative options. Private-public research partnerships have been established to promote expedited, cost-effective research. While most antivirals treat viral infection, vaccines are a preemptive first line of defense against pathogens. Vaccination involves the introduction of a small amount of inactivated or attenuated antigenic material to stimulate an individual's immune system; the immune system responds by developing white blood cells to combat the introduced pathogen, resulting in adaptive immunity.

Vaccination in a population results in herd immunity and improved population health, with significant reductions in viral infection and disease. Vaccination policy in the United States consists of private vaccination requirements. For instance, public schools require students to receive vaccinations (termed "vacc

Nick Percival is a British graphic artist and graphic novelist known for his published comic book, concept artwork and career in computer animation directing. Percival's first published work was in the monthly British comic Judge Dredd Megazine with a horror'strange cases' tale written by Dave Stone. After several similar stories in the Megazine, he went on to paint a nine-part story set in Judge Dredd's world in the Cursed Earth with the series Sleeze'n' Ryder, where Nick worked with acclaimed writer Garth Ennis; the pair would work together again for the British weekly comic 2000 AD on the Judge Dredd epic "Goodnight Kiss", another tale set in the radioactive wasteland of the Cursed Earth, where Judge Dredd is hunted by the assassin Jonni Kiss and the mutant Brotherhood of Marshalls. Percival painted the Sláine story "King of Hearts" for 2000 AD, where he worked with the co-creator of 2000 AD, Pat Mills. Aside from his 2000 AD work on various stories and painted covers, including a Dredd one-off story "Crime Prevention" with acclaimed comic book author Mark Millar, Percival has produced work for Marvel Comics, MTV, Wizards of the Coast, Upper Deck Entertainment, Boom!

Studios, IDW Publishing, Electronic Arts, Warner Bros. Activision, Sci Fi Channel, History Channel and Fantasy Flight Games, he became prolific in the video game and animation industries where he ran an animation studio in the UK. He directed computer generated cut-scenes for video game such as Men in Black II: Alien Escape, Z: Steel Soldiers, Carmageddon TDR 2000, the Games Workshop licensed video game of Gorkamorka, his company developed their own computer generated short films and Percival presented one of these at the Cartoon Movie Festival 2002 in Berlin. Percival is the author and illustrator of Legends: The Enchanted, an original graphic novel, to be adapted into a feature film by Ron Howard's Imagine Entertainment. Legends: The Enchanted won the HorrorNews Net award for Best Original Graphic Novel 2010. and was nominated for an Eagle Award for Favourite Single Story 2010. In 2015, Percival won the 13th Annual Rondo Hatton Classic Horror Award for Best Cover Art for his painted Nightbreed cover for Fangoria magazine.

Percival poster artwork for the independent horror film Female Werewolf won the Fantastic Cinema Excellence in Poster Design Award 2016. Percival is developing new projects for films, TV and video games and has completed an original new graphic novel series, The Family. In 2017, he won the Horror News Network's Comic Award for Best Cover Artwork of 2017 for the comic book Hookjaw. More Percival has been painting the continuing saga of Judge Dredd's most famous nemesis, Judge Death and the Dark Judges, with the Dark Justice: Dominion and The Torture Garden series. Interior comics artwork includes: Strange Cases: "Monsters" "The Great Outdoors" "Where the Heart is!" Sleeze'n' Ryder Brit-Cit Brute: "Brit-Cit Brute" "Trilogy" The Clown Book 2 Judge Dredd: "Judge Dredd: Crime Prevention" "Judge Dredd: Goodnight Kiss" "Judge Dredd: When Judges Go Bad" "Judge Dredd: The Complete Case Files" Volume 20 "Judge Dredd: The Complete Case Files" Volume 23 "Judge Dredd: Trauma Town" "Judge Dredd: The Mega Collection" #7, 22, 68 "Judge Dredd: The Gyre" "Judge Dredd: The Harvest" Vector 13: "Case Five: Shadrach" Marvel:Portraits of a Universe #1: Sláine: "King of Hearts" Slaine: "Demon Killer" Slaine: "The Grail War" Slaine: "2000AD The Ultimate Collection" Slaine Volume 5, trade hardback, 2019) Dead of Night: Featuring Man-Thing Legends: The Enchanted Legends: The Enchanted #0 The Family: Volume One Mean Machine Angel: Tales from the Black Museum Dark Souls: Legends of the Flame #1: The Labyrinth Dark Souls: Legends of the Flame #2: Action Reply Hellraiser: Anthology Volume 1, 2 Dark Judges: Dominion Dark Judges: The Torture Garden (with writer David Hine

Terry Hoff is an American painter. Hoff’s work is inspired by his youth spent immersed in California suburban culture. Terry Hoff was born in Arizona, he attended school at San Joaquin Delta College in Stockton and the Academy of Art University in San Francisco, where he teaches. Terry lives seaside in California, his work has been exhibited widely: 2007 - Thrill rides and home gardening, Andrea Schwartz Gallery, SF, CA 2005 - Homey, Andrea Schwartz Gallery, SF, CA 2004 - Bump, Heidi Cho Gallery, NY, NY 2003 - All you have to do is find your way home from here, Acuna-Hansen Gallery, LA, CA 2002 - Sleepyhead, Lizabeth Oliveria Gallery, SF, CA 2000 - Some Drawing, Acuna-Hansen Gallery, LA, CA 1999 - Nudge, Berkeley, CA 1998 - Pucker, RARE Gallery, NY, NY 1996 - Silly, Four Walls, SF, CA 1996 - Luggage Store Gallery, SF, CA 1996 - SF MOMA Rental Gallery, SF, CA 1996 - Four Walls, SF, CAHe has received several awards for his work: 1999 Eureka Fellowship from the Fleishhacker Foundation 1999 SECA Award finalist SF MOMA 1995 California Discovery Gold Award 1994 Grand Award San Diego Art InstituteTerry Hoff's work has been discussed and reviewed: The face of existential angst?

Or just plain silly? SF Chronicle, April 21, 2007 A look beyond the veneer of alleged innocent era. SF Chronicle, July 23, 2005 Terry Hoff at Lizabeth Oliveria. San Francisco Chronicle, January 25, 2003 Toying With Meaning. San Francisco Chronicle, 17 June 2000 Terry Hoff Pulls on the Emotions. SF Chronicle, 21 May 1998 Quick Draw Artists and Tender Hearts. San Francisco Chronicle, 13 June 1997 Stacking Things Up. San Francisco Chronicle, 11 December 1996 Exhibition Catalog, San Francisco, CA: Yerba Buena Center for the Arts, 1997 Eureka Exhibition Much Improved. San Francisco Chronicle, 1 February 2001 Gallery Watch. San Francisco Examiner, 18 December 1998 The Young at Art. San Francisco Examiner, 18 June 1997 Fellowship Awards. Exhibition Catalog, San Jose Museum of Art, 2000–2001 Artists To Keep An Eye On. San Jose Mercury News, 14 January 2001 Twisted Visions of Youth. San Jose Mercury News, 1 February 2004 Over There. East Bay Express, 10 October 1997 Candyland. San Francisco Bay Guardian, 13 June 1998 Nickel-Angelo.

San Francisco Bay Guardian, 26 November 1997 Dispatches. Sculpture: pp. 68-69 Terry Hoff at Lizabeth Oliveria Gallery. Artweek, March 17, 2003 Exhibition Catalog. Newcastle upon Tyne, UK: Laing Art Gallery, 2000 Sugar Fix. San Francisco Bay Guardian, 25 June 1997 Three Painters. San Francisco Bay Guardian, 22 May 1996 Leo Bersamina, Patricia Hagen and Terry Hoff. Artweek 27: p. 21 Terry Hoff's Web Site