Flaviviruses PDF

Flaviviruses Flaviviridae Flavivirus: hemorrhagic fever, encephalitis, and the birth defect microcephaly Hepacivirus : hepatitis Pegivirus ??? "Pe" stands for "persistent" and "g" is a reference to Hepatitis G, Pestivirus: hemorrhagic syndromes, fatal mucosal disease The Flaviviridae are a family...

Flaviviruses Flaviviridae Flavivirus: hemorrhagic fever, encephalitis, and the birth defect microcephaly Hepacivirus : hepatitis Pegivirus ??? "Pe" stands for "persistent" and "g" is a reference to Hepatitis G, Pestivirus: hemorrhagic syndromes, fatal mucosal disease The Flaviviridae are a family of positive, single-stranded, enveloped RNA viruses. They are found in arthropods, (primarily ticks and mosquitoes), and can occasionally infect humans. flavus is Latin for "yellow Flavivirus This genus consists primarily of >50 species of arthropod- borne viruses, with distinct groups infecting mosquitoes or ticks. Mammals and birds are the usual primary hosts, in which infections range from asymptomatic to severe or fatal haemorrhagic fever or neurological disease. Important human pathogens include yellow fever virus, dengue virus, Japanese encephalitis virus, West Nile virus and tick-borne encephalitis virus. Other members cause economically important diseases in domestic or wild animals. Additional viruses infecting only arthropods or only mammals (e.g. Tamana bat virus) have been described recently. mosquitoes-transmitted viruses include: Yellow Fever, Dengue Fever, Japanese encephalitis, West Nile viruses, and Zika virus. transmitted by ticks and are responsible of encephalitis and hemorrhagic diseases: Tick-borne Encephalitis (TBE), Kyasanur Forest Disease (KFD) and Alkhurma disease, and Omsk hemorrhagic fever. Hepacivirus This genus includes hepatitis C virus, a major human pathogen causing progressive liver disease , and several other viruses of unknown pathogenicity that infect horses, rodents, bats, cows and primates. Infections are typically persistent and target the liver. Pegivirus Members are widely distributed in a range of mammalian species, in which they cause persistent infections. To date, they have not been clearly associated with disease. GB virus C (GBV-C), formerly known as hepatitis G virus (HGV) and also known as human pegivirus – HPgV is a virus GB Virus C (and indeed, GBV-A and GBV-B) is named after the surgeon, G. Barker, who fell ill in 1966 with a non-A non-B hepatitis which at the time was thought to have been caused by a new, infectious hepatic virus Pestivirus These viruses infect pigs and ruminants, including cattle, sheep, goats and wild ruminants, and are transmitted through contact with infected secretions (respiratory droplets, urine or faeces). Infections may be subclinical or cause enteric, haemorrhagic or wasting diseases, including those by the economically important bovine viral diarrhoea virus and classical swine fever virus. The yellow fever virus is found in tropical and subtropical areas of Africa and South America. The virus is spread to people by the bite of an infected mosquito. Illness ranges from a fever with aches and pains to severe liver disease with bleeding and yellowing skin (jaundice). Yellow fever infection is diagnosed based on laboratory testing, a person’s symptoms, and travel history. There is no medicine to treat or cure infection. To prevent getting sick from yellow fever, use insect repellent, wear long- sleeved shirts and long pants, and get vaccinated. Yellow Fever Vaccine A safe and effective yellow fever vaccine has been available for more than 80 years. A single dose provides lifelong protection for most people. The vaccine is a live, weakened form of the virus given as a single shot. Vaccine is recommended for people aged 9 months or older and who are traveling to or living in areas at risk for yellow fever virus in Africa and South America. Yellow fever vaccine may be required for entry into certain countries. Reactions to Yellow Fever Vaccine Reactions to yellow fever vaccine are generally mild and include headaches, muscle aches, and low-grade fevers. Rarely, people develop severe, sometimes life-threatening reactions to the yellow fever vaccine, including: Allergic reaction, including difficulty breathing or swallowing (anaphylaxis) Swelling of the brain, spinal cord, or the surrounding tissues (encephalitis or meningitis) Guillain-Barré syndrome, an uncommon sickness of the nervous system in which a person’s own immune system damages the nerve cells, causing muscle weakness, and sometimes, paralysis. Internal organ dysfunction or failure Dengue viruses are spread to people through the bite of an infected Aedes species (Ae. aegypti or Ae. albopictus) mosquito. These mosquitoes also spread Zika, chikungunya, and other viruses. Dengue is common in more than 100 countries around the world. Forty percent of the world’s population, about 3 billion people, live in areas with a risk of dengue. Dengue is often a leading cause of illness in areas with risk. Each year, up to 400 million people get infected with dengue. Approximately 100 million people get sick from infection, and 22,000 die from severe dengue. Dengue is caused by one of any of four related viruses: Dengue virus 1, 2, 3, and 4. For this reason, a person can be infected with a dengue virus as many as four times in his or her lifetime. Dengue epidemics tend to have seasonal patterns, with transmission often peaking during/after rainy seasons. There are several factors contributing to this increase and they include: high mosquito population levels, susceptibility to circulating serotypes, favourable air temperatures, precipitation and humidity all of which affect the reproduction and feeding patterns of mosquito populations, as well as the dengue virus incubation period. From mother to child A pregnant woman already infected with dengue can pass the virus to her fetus during pregnancy or around the time of birth. To date, there has been one documented report of dengue spread through breast milk. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas with risk of dengue. Symptoms and Treatment 1 in 4: About one in four people infected with dengue will get sick. For people who get sick with dengue, symptoms can be mild or severe. Severe dengue can be life-threatening within a few hours and often requires hospitalization. Symptoms Mild symptoms of dengue can be confused with other illnesses that cause fever, aches and pains, or a rash. The most common symptom of dengue is fever with any of the following: Nausea, vomiting Rash Aches and pains (eye pain, typically behind the eyes, muscle, joint, or bone pain) Any warning sign see next slide Symptoms of dengue typically last 2–7 days. Most people will recover after about a week. Warning signs of severe dengue Watch for signs and symptoms of severe dengue. Warning signs generally begin in the 24–48 hours after your fever has gone away. If you or a family member develops any of the following symptoms, immediately go to a local clinic or emergency room: Stomach or belly pain, tenderness Vomiting (at least 3 times in 24 hours) Bleeding from the nose or gums Vomiting blood, or blood in the stool Feeling tired, restless, or irritable Severe dengue About 1 in 20 people who get sick with dengue will develop severe dengue. Severe dengue is a more serious form of disease that can result in shock, internal bleeding, and even death. You are more likely to develop severe dengue if you have had a dengue infection before. Infants and pregnant women are at increased risk for developing severe dengue Treatment There is no specific medication to treat dengue. Treat the symptoms of dengue See a healthcare provider if you develop a fever or have symptoms of dengue. Tell him or her about your travel. Rest as much as possible. Take acetaminophen to control fever and relieve pain. – Do not take aspirin or ibuprofen! Drink plenty of fluids such as water or drinks with added electrolytes to stay hydrated. For mild symptoms, care for a sick person at home. Treatment of severe dengue If you develop any warning signs, see a healthcare provider or go to the emergency room immediately. Severe dengue is a medical emergency and requires immediate medical attention or hospitalization.  The best way to prevent these diseases is to protect yourself from mosquito bites. (we discussed this earlier) If You Have Dengue, Protect Others During the first week of infection, dengue virus is found in the blood of an infected person. If a mosquito bites the infected person, the mosquito becomes infected. The infected mosquito can spread the virus to other people through bites. Not everyone infected with dengue gets sick. Even if you do not feel sick, travelers returning home from an area with risk of dengue should take steps to prevent mosquito bites for 3 weeks so they do not spread dengue to mosquitoes that could spread the virus to other people. Dengue Vaccine Dengue vaccine is a vaccine used to prevent dengue fever in humans. As of 2019, one version is commercially available, known as CYD-TDV, and sold under the brand name Dengvaxia A vaccine to prevent dengue (Dengvaxia®) is licensed and available in some countries for people ages 9-45 years old. The World Health Organization recommends that the vaccine only be given to persons with confirmed prior dengue virus infection. The vaccine manufacturer, Sanofi Pasteur, announced in 2017 that people who receive the vaccine and have not been previously infected with a dengue virus may be at risk of developing severe dengue if they get dengue after being vaccinated Dengue vaccine use is complicated by the fact that virus occurs in four serotypes, and immunity against any one serotype does not generate lasting immunity against the other three, hence the need for a tetravalent vaccine. Furthermore, being infected with—and developing immunity to—one viral serotype seems to be the trigger that can lead to a patient having more severe disease manifestations when subsequently infected with a different serotype, a phenomenon known as antibody-dependent enhancement. Question: How to treat haemorrhage resulting from Dengue fever? What is immune enhacement? Japanese encephalitis (JE) virus is the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. For most travelers to Asia, the risk for JE is very low but varies based on destination, length of travel, season, and activities. Most people infected with JE do not have symptoms or have only mild symptoms. However, a small percentage of infected people develop inflammation of the brain (encephalitis), with symptoms including sudden onset of headache, high fever, disorientation, coma, tremors and convulsions. About 1 in 4 cases are fatal. 30%-50% of survivors continue to have neurologic, cognitive, or psychiatric symptoms. To prevent getting sick from JE, use an EPA-registered insect repellent, wear long-sleeved shirts and long pants, and get vaccinated. West Nile virus (WNV) is the leading cause of mosquito- borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness. You can reduce your risk of WNV by using insect repellent and wearing long-sleeved shirts and long pants to prevent mosquito bites. West Nile Virus & Dead Birds West Nile virus has been detected in variety of bird species. Some infected birds, especially crows and jays, are known to get sick and die from the infection. Reporting and testing of dead birds is one way to check for the presence of West Nile virus in the environment. Some surveillance programs rely on citizens to report dead bird sightings to local authorities. Zika Zika is spread mostly by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). Zika can be passed from a pregnant woman to her fetus. Through sex Through blood transfusion (very likely but not confirmed) Infection during pregnancy can cause certain birth defects. There is no vaccine or medicine for Zika.  Many people infected with Zika virus won’t have symptoms or will only have mild symptoms. The most common symptoms of Zika are Fever Rash Headache Joint pain Red eyes Muscle pain Symptoms can last for several days to a week. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. Once a person has been infected with Zika, they are likely to be protected from future infections. Zika infection during pregnancy can cause a birth defect of the brain called microcephaly and other severe brain defects. It is also linked to other problems, such as miscarriage, stillbirth, and other birth defects. There have also been increased reports of Guillain- Barré syndrome, an uncommon sickness of the nervous system, in areas affected by Zika. How Zika is diagnosed Diagnosis of Zika is based on a person’s recent travel history, symptoms, and test results. A blood or urine test can confirm a Zika infection. Symptoms of Zika are similar to other illnesses spread through mosquito bites, like dengue and chikungunya.  There is no specific medicine or vaccine for Zika virus. Treat the symptoms: Get plenty of rest. Drink fluids to prevent dehydration. Take medicine such as acetaminophen to reduce fever and pain. Do not take aspirin or other non-steroidal anti- inflammatory drugs (NSAIDs). If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional me Prevention? Home work for moodle Louping-ill is an acute viral disease primarily of sheep that is characterized by a biphasic fever, depression, ataxia, muscular incoordination, tremors, posterior paralysis, coma, and death. Louping-ill is a tick-transmitted disease. It also causes disease in humans. The name 'louping-ill' is derived from an old Scottish word describing the effect of the disease in sheep whereby they 'loup' or spring into the air. Kyasanur Forest disease (KFD) is caused by Kyasanur Forest disease virus (KFDV), a member of the virus family Flaviviridae. KFDV was identified in 1957 when it was isolated from a sick monkey from the Kyasanur Forest in Karnataka (formerly Mysore) State, India. Since then, between 400-500 humans cases per year have been reported. Hard ticks (Hemaphysalis spinigera) are the reservoir of KFD virus and once infected, remain so for life. Rodents, shrews, and monkeys are common hosts for KFDV after being bitten by an infected tick Alkhurma hemorrhagic fever (AHF) is caused by Alkhurma hemorrhagic fever virus (AHFV), a tick-borne virus of the Flavivirus family. The virus was initially isolated in 1995 from a patient in Saudi Arabia. Subsequent cases of AHF have been documented in tourists in Egypt, extending the geographic range of the virus and suggesting that geographic distribution of the virus is wide and that infections due to AHFV are underreported. The persistence of the virus within tick populations, and the role of livestock in the disease transmission process, are not well understood. The AHFV virus is a variant of Kyasanur Forest Disease (KFD) Since the first description of AHFV, several hundred cases of AHF have been reported. Cases appear to peak in spring and summer. Further study of AHFV is needed to improve public health measures.  Omsk hemorrhagic fever (OHF) is caused by Omsk hemorrhagic fever virus (OHFV), a member of the virus family Flaviviridae. OHF was described between 1945 and 1947 in Omsk, Russia from patients with hemorrhagic fever. Rodents serve as the primary host for OHFV, which is transmitted to rodents from the bite of an infected tick What is hepatitis C? Hepatitis C is a liver infection caused by the hepatitis C virus. Hepatitis C can range from a mild illness lasting a few weeks to a serious, lifelong illness. Hepatitis C is often described as “acute,” meaning a new infection or “chronic,” meaning lifelong infection. Acute hepatitis C occurs within the first 6 months after someone is exposed to the hepatitis C virus. Hepatitis C can be a short-term illness, but for most people, acute infection leads to chronic infection. Chronic hepatitis C can be a lifelong infection with the hepatitis C virus if left untreated. Left untreated, chronic hepatitis C can cause serious health problems, including liver damage, cirrhosis (scarring of the liver), liver cancer, and even death. What is the likelihood that acute hepatitis C will become chronic? Approximately 75%–85% of people who become infected with hepatitis C virus will develop a chronic infection. Is it possible to clear the hepatitis C virus? Yes, approximately 15%–25% of people who are infected with the hepatitis C virus clear it from their bodies without treatment and do not develop chronic infection. Experts do not fully understand why this happens for some people.  Today, most people become infected with the hepatitis C virus by sharing needles or other equipment to prepare or inject drugs. Before 1992, hepatitis C was also commonly spread through blood transfusions and organ transplants. After that, widespread screening of the blood supply virtually eliminated this source of infection.  People can become infected with the hepatitis C virus during such activities as: - Sharing needles, syringes, or other equipment to prepare or inject drugs - Needlestick injuries in health care settings - Being born to a mother who has hepatitis C Less commonly, - Sharing personal care items that may have come in contact with another person’s blood, such as razors or toothbrushes - Having sexual contact with a person infected with the hepatitis C virus - Getting a tattoo or body piercing in an unregulated setting Can I be re-infected with hepatitis C virus if I have cleared the virus? Yes. If you have been infected with the hepatitis C virus and cleared the virus, or if you have been successfully treated and cured, you can be re- infected with the hepatitis C virus. There are 8? 11? genotypes and 70? subtype Genotypes are not only crucial for our understanding of the epidemiology and evolution of HCV; they are clinically significant as current treatment regimens are tailored to the infecting genotype There is no antigenic cross protection between genotypes (hard for treatment and vaccine) What is the risk of a pregnant woman passing hepatitis C to her baby? About 6 in 100 infants born to mothers with hepatitis C become infected with the hepatitis C virus. However, the risk becomes greater if the mother has both HIV and hepatitis C. What are the symptoms of acute hepatitis C? People with new (acute) hepatitis C virus infection usually do not have symptoms or have mild symptoms. When symptoms do occur, they can include: Fever Fatigue Dark urine Clay-colored bowel movements Abdominal pain Loss of appetite Nausea Vomiting Joint pain Jaundice (yellow color in the skin or eyes) How soon after exposure to hepatitis C virus do symptoms appear? In those people who develop symptoms from acute infection, the average time from exposure to symptoms ranges from 2 to 12 weeks. However, most people who are infected with the hepatitis C virus do not develop symptoms. What are the symptoms of chronic hepatitis C? Most people with chronic hepatitis C virus infection do not have any symptoms or have general, or common symptoms such as chronic fatigue and depression. Many people eventually develop chronic liver disease, which can range from mild to severe, including cirrhosis (scarring of the liver) and liver cancer. Chronic liver disease in people with hepatitis C usually happens slowly, without any signs or symptoms, over several decades. Chronic hepatitis C virus infection is often not recognized until people are screened for blood donation or from an abnormal blood test found during a routine examination. What are the long-term effects of hepatitis C? Of every 100 people infected with hepatitis C virus: 75-85 will develop chronic infection 10-20 will develop cirrhosis over 20-30 years Among 100 people with hepatitis C and cirrhosis, with each passing year: 3-6 will develop liver failure 1-5 will develop liver cancer Developing cirrhosis is more likely if you are male, age 50 years and older, use alcohol, have nonalcoholic fatty liver disease, hepatitis B virus or HIV coinfection, or take immunosuppressive drugs. Who should get tested for hepatitis C? Current or former injection drug users, including those who injected only once many years ago Everyone born from 1945 to 1965 Anyone who received clotting factor concentrates made before 1987 Recipients of blood transfusions or solid organ transplants prior to July 1992 Long-term hemodialysis patients People with known exposures to the hepatitis C virus, such as – health care workers or public safety workers after needle sticks involving blood from someone infected with hepatitis C virus – recipients of blood or organs from a donor who tested positive for the hepatitis C virus People with HIV infection Children born to mothers with hepatitis C People in jails or prisons People who use drugs snorted through the nose (in addition to people who inject drugs), People who get an unregulated tattoo Should a woman with hepatitis C virus infection avoid breastfeeding? No. There is no evidence that breastfeeding spreads hepatitis C virus. Precautions may be considered if a mothers with hepatitis C has cracked or bleeding nipples because there is not enough information on the risks of transmission when this happens. What is the treatment for acute hepatitis C? There is not a recommended treatment for acute hepatitis C. People with acute hepatitis C virus infection should be followed by a doctor and only considered for treatment if their infection remains and becomes a chronic infection. What is the treatment for chronic hepatitis C? There are several medications available to treat chronic hepatitis C. Hepatitis C treatments have gotten much better in recent years. Current treatments usually involve just 8-12 weeks of oral therapy (pills) and cure over 90% of people with few side effects No interferon any more  HCV can mutate in-vivo thus escaping the immune surveillance Pegivirus Members are widely distributed in a range of mammalian species, in which they cause persistent infections. To date, they have not been clearly associated with disease. GB virus C (GBV-C), formerly known as hepatitis G virus (HGV) and also known as human pegivirus – HPgV is a virus GB Virus C (and indeed, GBV-A and GBV-B) is named after the surgeon, G. Barker, who fell ill in 1966 with a non-A non-B hepatitis which at the time was thought to have been caused by a new, infectious hepatic virus  Hepatitis G= Human pegivirus (HPgV), formally called GB virus C (GBV-C) Around 750 million persons have HPgV viremia and the virus is transmitted by blood, sex and birth The virus has some benefits since the life of HIV infected persons may be prolonged if they are co- infected with HPgV