RCSB PDB, 2008 About dengue virus and how it infects humans to cause dengue fever.
RCSB PDB, 2008 Elelctron micrograph showing the structure of dengue virus
RCSB PDB, 2008 Areas in the world that are affected by dengue viral fever are shown in red
Measles is a viral infection with an incubation period of 8-14 days. It is uncommon in the first year of life. Starts with running nose, reddened watery eyes, cough and rising temperature. White (Koplik) spots appear on inside of cheeks on 3rd-4th day. A blotchy red rash starts behind ears and spreads to face and body. Measles is a potentially serious illness, which can include high fever, and complications such as eye and middle ear infection, deafness, croup, pneumonia and, more rarely, brain damage. Call the doctor. Keep child cool. Give plenty of drinks, and a prescribed dose of paracetamol to reduce fever. Call doctor again if further symptoms develop. Poliomyelitis and its symptoms: Poliomyelitis (polio) is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. The virus enters the body through the mouth and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5%–10% die when their breathing muscles become immobilized. Persons at risk of polio: Polio mainly affects children under five years of age. In 1988, the forty-first World Health Assembly, consisting then of delegates from 166 Member States, launched a global initiative to eradicate polio by the end of the year 2000. This followed the certification of the eradication of smallpox in 1980, progress during the 1980s towards elimination of the poliovirus in the Americas, and Rotary International’s commitment to raise funds to protect all children from the disease. Progress: Overall, in the 15 years since the Global Polio Eradication Initiative was launched, the number of cases has fallen by over 99%, from an estimated more than 350 000 cases in 1988 to 1919 reported cases in 2002 (as of 16 April 2003). In the same time period, the number of polio-infected countries was reduced from 125 to 7. In 1994, the World Health Organization (WHO) Region of the Americas (36 countries) was certified polio-free, followed by the WHO Western Pacific Region (37 countries and areas including China) in 2000 and the WHO European Region (51 countries) in June 2002. Widely endemic on five continents in 1988, polio is now found only in parts of Africa and south Asia. Progress from 2001 to 2002 includes a reduction in polio-endemic countries from ten to seven. Over 500 million children were immunized in 93 countries during 266 supplementary immunization activities (SIAs). Globally, polio surveillance improved in 2002, as reflected in an increase in acute flaccid paralysis (AFP) rates from 1.6 in 2001 to 1.9 in 2002, representing even better detection of AFP cases. Despite these achievements, the Polio Eradication Initiative faced an increase in global cases in 2002 over 2001. In 2002, 1919 cases were reported (as of 16 April 2003), compared to 483 in 2001. This increase can be attributed to an epidemic in India, and a further increase in cases in Nigeria.
Diseases Caused by Viruses viruses are everywhere in nature, but only a few cause disease
Also important…Any agent (not just viruses) that causes disease is a pathogen.When a virus inserts its genetic material into a host’s DNA, it is called a provirus.Some viruses replicate very slowly and only cause damage when the conditions are “right”. (cold sores)
Viruses are host cell specific. Most viruses are restricted to certain kinds of cells (those that infect plants cannot infect animal cells). Why? Scientists think that viruses originated from escaped genetic material from host cells.
Viruses can be beneficial…Bacteriophages – attack & destroy bacteriaBaculovirus – ebola-like virus that attacks insects – Could use for pest control in crops • Cabbage loopers eat cabbage crops • Virus can kill pests in days – (it’s really gross) … and then there are those that are not so good….
RNA or DNA?Viruses with RNA – Human immunodeficiency virus (HIV) – Influenza viruses – RabiesViruses with DNA – Warts – Chickenpox – mononucleosis
Retroviruses• Contain RNA instead of DNA• Copy their RNA into DNA instead of DNA to RNA• Examples: AIDS, some cancers
Viral Disease in Humans • Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium • Unlike bacterial diseases, viruses can’t be treated with antibiotics • The best way to protect against most viral diseases lies in prevention by the use of vaccines
Viral Disease in Animals • Viruses produce serious animal disease as well • Ex.) Foot-and-mouth disease, Rous sarcoma
Viral Disease in Plants • Many viruses infect plants • Ex.) Tobacco mosaic virus, potato yellow dwarf virus
Viruses are responsible for a number of plant diseases • Approximately 2,000 kinds of plant diseases have been attributed to viruses – Plant viruses are responsible for the loss of over 15 billion dollars annually by reducing the yield of important agricultural and horticultural crops • Once a plant is infected the virus spreads slowly throughout the plant • In some instances, plants have been purposefully infected with a virus in order to produce traits considered desirable by gardeners • Example: Some variegation in leaves and flowers can be brought about by viruses 16-13
A virus is responsible for the variegation and streaking inRembrandt tulips
Viroids and Prions • Scientists have discovered two virus-like particles that also cause disease
Viroids• Single stranded RNA molecules that have no surrounding capsid• Cause disease in plants
Prions• Proteins that cause disease in animalsEx.) Mad cow disease
Surgical masks provide protection againstthe transmission of SARS 16-21
Exterminating possibly infected chickens may protectagainst bird flu 16-22
A provirus is a DNA virus that has been inserted into ahost cell chromosome.
Human Immunodeficiency Virus (HIV) Acquired Immuno Deficiency Syndrome (AIDS)
How Is HIV Spread? • Sexual contact • Sharing contaminated needles • Blood transfusions • Breast feeding (mother to baby) • Mother to baby during pregnancy or birth
• HIV is a retrovirus injecting the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA.
Viruses are host specific – a protein on the surface of thevirus has a shape that matches a molecule in the plasmamembrane of its host, allowing the virus to lock onto thehost cell.
• HIV doesn’t target just any cell, it goes right for the cells that want to kill it. “Helper" T cells are HIVs primary target. These cells help direct the immune systems response to various pathogens.
HIV undermines the bodys ability toprotect against disease by depleting Tcells thus destroying the immunesystem. After many years ofinfect 10 battle, the body has The virus can a constant billion cells ainsufficient only 1.8 billion to mount an immuneday, yet numbers of T-Cells can be replacedresponse against infections. At the point when thedaily.body is unable to fight off infections, a person is said to have the disease AIDS.It is not the virus or the disease that ultimately kills a person; it is the inability to fight off something as minor as the common cold.
Think about it…• In the US, there is better than a 1/1000 chance of contracting HIV during unprotected sex• A person can be contagious for more than 10 years before any sign of the disease is apparent• HIV becomes AIDS when the number of immune cells drops below a predetermined number• No one dies from HIV or AIDS; people die from secondary infections (ranging from the common cold to cancer)• More than 3 million people (size of Chicago) die each year • There are approx. 14,000 new cases of HIV worldwide every day
Viral Hepatitis - Overview Type of Hepatitis A B C D ESource of feces blood/ blood/ blood/ fecesvirus blood-derivedblood-derived blood-derived body fluids body fluids body fluidsRoute of fecal-oral percutaneouspercutaneous percutaneous fecal-oraltransmission permucosal permucosal permucosalChronic no yes yes yes noinfectionPrevention pre/post- pre/post- blood donor pre/post- ensure safe exposure exposure screening; exposure drinking immunization immunization risk behavior immunization; water modification risk behavior modification
Introduction• approximately 350 million people are infected globally with HBV.
High-risk groups for HBV infection • People from endemic regions • Babies of mothers with chronic HBV • Intravenous drug abusers • People with multiple sex partners • Hemophiliacs and other patients requiting blood and blood product treatments • Health care personnel who have contact with blood • Residents and staff members of institutions for the mentally retarded
Treatment• Interferon-alpha may be effective for treating a chronic HBV infection.• Hepatitis B immune globulin may be administered within a week of exposure and to newborn infants of HBsAg-positive mothers.
Introduction• The major cause of parenterally transmitted non A non B hepatitis. It eluded identification for many years. In 1989, the genome was cloned from the serum of an infected chimpanzee.
Transmission• Blood transfusions, blood products• organ donation• Intravenous drug abusers• community acquired: mechanism unclear. ?• Vertical transmission ?• sexual intercourse
Chronic Hepatitis CFactors Promoting Progression orSeverity • Increased alcohol intake • Age > 40 years at time of infection • HIV co-infection • ?Other – Male gender – Other co-infections (e.g., HBV)
Treatment, Prevention,and Control • Recombinant interferon-alpha is the only known effective treatment for HCV. • Illicit drug abuse and transfusion are the most identifiable sources of HCV viruses.