MCB 404: Medical Virology PDF

AMBROSE ALLI UNIVERSITY, EKPOMA MICROBIOLOGY DEPARTMENT MCB 404: MEDICAL VIROLOGY SOME MEDICALLY IMPORTANT RNA VIRUSES ARBOVIRUSES Arbovirus is a term used to describe a group of viral infections t...

AMBROSE ALLI UNIVERSITY, EKPOMA MICROBIOLOGY DEPARTMENT MCB 404: MEDICAL VIROLOGY SOME MEDICALLY IMPORTANT RNA VIRUSES ARBOVIRUSES Arbovirus is a term used to describe a group of viral infections transmitted to humans from a group of insects known as arthropods. Insects that can infect humans with arboviruses include fleas, ticks, and mosquitoes. Three main genera for arboviruses that cause infections in humans. Flavivirus- Yellow fever, West Nile virus. Zika virus, Dengue fever, Japanese encephalitis Togavirus - Ross River virus, Eastern equine virus, Western equine virus Bunyavirus- California encephalitis, La Crosse virus, Jamestown Canyon virus TRANSMISION Through insect bite and spread through blood transfusion, organ transplant, sexual contact, pregnancy and childbirth from mother to child. CLINICAL FEATURES Neuroinvasive diseases- Causes meningitis, fever headache, stiff neck, muscle pain, confusion or disorientation, weakness in the arms and legs, seizures. Non-neuroinvasive- Causes fever, headache, muscle aches, joint pain, upset stomach, nausea, vomiting, or diarrhea, rash. EPIDEMIOLOGY They have a global distribution. The warm climate conditions found in tropical areas allows for year-round transmission by the arthropod vectors DIAGNOSIS ELISA, Polymerase chain reaction (PCR) 1 TREATMENT Treatment for most of these infections is supportive. PREVENTION AND CONTROL Vaccines are available for some arboviruses, including Japanese encephalitis and yellow fever, there is not a vaccine for all arboviruses. Prevent insect bites by: using insect repellant, wearing clothing that covers the limbs when outdoors, tucking pants into socks, wearing light colored clothing, so that insects are easy to spot. CORONAVIRUSES Coronaviruses are a large family of respiratory viruses that includes COVID-19, Middle East Respiratory Syndrome (MERS), and Severe Acute Respiratory Syndrome(SARS). Coronaviruses cause diseases in animals and humans. They often circulate among camels, cats, and bats, and can sometimes evolve and infect people. In humans, the viruses can cause mild respiratory infections, like the common cold, but can lead to serious illnesses, like pneumonia. COVID-19, the novel coronavirus (SARS-CoV-2) that causes COVID-19 first emerged in the Chinese city of Wuhan in 2019 and was declared a pandemic by the World Health Organization (WHO). In December 2020, the US launched a national vaccination campaign. There are steps you can take to help stop the spread of COVID-19, including getting vaccinated. TRANSMISSION Infected carriers are able to shed viruses into the environment. The interaction of the coronavirus spike protein with its complementary cell receptor is central in determining the tissue tropism, infectivity, and species range of the released virus. Human coronaviruses can be spread primarily through: coughing and sneezing, close personal contact, such as touching or shaking hands, touching an object or surface with the virus on it, then touching your mouth, nose, or eyes CLINICAL FEATURES 2 These illnesses usually last for a short amount of time, and symptoms may include: Fever, Cough headache, runny nose, sore throat, pneumonia or bronchitis (among individuals with weakened immune system, infants older adults and those with lungs and heart disease). EPIDEMIOLOGY The epidemiology of coronavirus colds has been little studied. Waves of infection pass through communities during the winter months, and often cause small outbreaks in families, schools. Immunity does not persist, and subjects may be re-infected, sometimes within a year. The pattern thus differs from that of rhinovirus infections, which peak in the fall and spring and generally elicit long-lasting immunity. About one in five colds is due to coronaviruses. DIAGNOSIS ELISA, PCR TREATMENT Take pain and fever medications, use a humidifier or take a hot shower, drink plenty of liquids, stay home and rest. PREVENTION AND CONTROL There are steps you can take to help prevent infection: There are steps you can take to help prevent infection: Get vaccinated, wear a face mask, wash your hands with soap and water for at least 20 seconds, avoid touching your eyes, nose, or mouth cover coughs and sneezes with a tissue, clean and disinfect objects and surfaces, avoid close contact with people who are sick and stay home if you are sick. RETROVIRUSES A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own 3 genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus eg HIV virus, human T-lymphotropic virus (HTLV). Many retroviruses cause serious diseases in humans, other mammals, and birds. Retroviruses have many subfamilies in three basic groups. Oncoretroviruses (cancer-causing retroviruses) include human T-lymphotropic virus (HTLV) causing a type of leukemia in humans, and murine leukemia viruses (MLVs) in mice. Lentiviruses (slow viruses) include HIV-1 and HIV-2, the cause of acquired immune deficiency syndrome (AIDS) in humans. Spumaviruses (foamy viruses) are benign and not linked to any disease in humans or animals TRANSMISSION  The infection is spread primarily from mothers to their children (Vertical transmission), most commonly through childbirth or breast feeding.  A second common route of transmission is from Unprotected sexual contact – vaginal, anal or oral. infected men to women via virus-infected cells present in semen. Sexually mediated transmission from women to men does not appear to occur at a significant frequency.  The third common route of transmission of HTLV-1 is via blood or blood cell products, a mode of transmission that accounts for the high frequency of intravenous drug users that have become infected.  Medical procedures – blood products, skin grafts, organ donation and artificial insemination CLINICAL FEATURES The clinical features of HIV can be divided into the initial seroconversion illness and symptomatic HIV. Seroconversion Illness 2-6 weeks after exposure, patients may experience a non-specific, flu-like illness. Features include: Fever, Muscle aches, Malaise, Lymphadenopathy, Maculopapular rash, Pharyngitis Symptomatic HIV 4 After a latent phase, the HIV infection will become symptomatic. The patient may experience: Weight loss, High temperatures, Diarrhoea, Frequent minor opportunistic infections, e.g. herpes zoster or candidiasis. DIAGNOSIS ELISA. Polymerase Chain Reaction (PCR) TREATMENT Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. Different classes of antiretroviral drugs act on different stages of the HIV life cycle. Combination of several (typically three or four) antiretroviral drugs is known as highly active antiretroviral therapy (HAART). PREVENTION AND CONTROL Vaccine not yet available, Blood supply screening, Public education, Safer sex practices, Counseling for pregnant women,, Preexposure prophylaxis with antiretrovirals (PrEP), Screening of blood and organs. 5