The article below appeared in the April 12 issue of Health with Perdana, a regular column in The Star by Perdana University faculty members. This week’s article is contributed by Assoc. Prof. Dr. Mohammad Nazmul Hasan Maziz, Associate Professor in Medical Microbiology, Perdana University Graduate School of Medicine.
There are many viruses that can cause disease in humans, some that can be prevented by vaccination and many with no cure.
All of us are aware of the word “Virus” but how many of us actually know what virus is, how they come to our body, what disease they cause and how to treat them? In this article we will come across some of the common viruses which are prevalent in this region.
A virus is an obligate intracellular parasite. Virus particles can only be observed by an electron microscope. Most viruses range in sizes from 20-250 nanometers. Viruses cannot reproduce outside a host cell and they must use resources of the host cell in order to reproduce. Viruses do not have the genetic capability to multiply by division like bacteria do. Three main properties distinguish viruses from other microorganism: their small size, genome (which are either RNA or DNA but not both) and their total dependence upon a living cell.
We can see five basic structural forms of viruses in nature which are naked icosahedral, naked helical, enveloped icosahedra, enveloped helical and complex. Viruses are named based on the disease they cause, their discoverers, geographical locations and how they were originally thought to be contracted. Viruses enter our body by respiratory transmission, faecal-oral transmission, blood-borne transmission, sexual transmission and through animal or insect vectors. For most of the viral infections, there is no medicine needed. Our body’s immune system is enough to kill them. We must remember that, antibiotic is used for bacterial infections only, not for viral infections. Some of the medically important viruses are:
Herpes simplex virus is involved in a variety of clinical manifestations which includes acute gingivostomatitis, herpes labialis (cold sore), ocular herpes, herpes genitalis, meningitis, encephalitis and neonatal herpes. Varicella zoster infection results in varicella (chickenpox) that presents fever, lymphadenopathy and widespread vesicular rash. Herpes zoster causes zoster which is the manifestation of recurrent infection following a primary attack of chicken pox. Infection typically affects adults of middle age or over. Pain precedes the rash (vesicles). Shingles causes severe pain and commonly occurs on one side of the trunk. Cytomegalovirus
causes hepatosplenomegaly, jaundice, thrombocytopenic purpura, hemolytic anemia, microcephaly, cerebral calcifications and mental retardation. Epstein – Barr (EB) virus causes Burkitt’s lymphoma, infectious mononucleosis and nasopharyngeal carcinoma. Occurs in 80 – 90% of children by three years of age. Mostly asymptomatic, not highly contagious and droplets are not infectious.
Human Papillomavirus (HPV)
This virus is transmitted by direct contact. Most HPV infections cause no symptoms and resolve spontaneously. In some, they persist and result in warts or precancerous lesions. The precancerous lesions increase the risk of cancer of the cervix, vulva, vagina, mouth or throat. HPV infection of the skin in the genital area is the most common sexually transmitted infection worldwide. No antiviral therapy but the HPV vaccines can prevent the most common types of infection.
Human immunodeficiency virus (HIV)
HIV is transmitted by sexual contact, blood transfusion, contaminated needles and transplacental- during delivery. It attacks our immune cells (CD4+) and lowers its count progressively and the patient becomes immunocompromised. This condition is known as Acquired Immune Deficiency Syndrome (AIDS). Patients will have multiple non-specific conditions such as persistent generalized lymphadenopathy, diarrhea, chronic fevers, night sweats and weight loss. This virus is treated with anti-retroviral drugs such as reverse transcriptase inhibitors, protease inhibitors, Highly Active Antiretroviral Therapy (HAART)- nucleoside analog reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and protease inhibitors. There’s no vaccine to prevent HIV infection and no cure for AIDS. Screening before blood transfusion, safer sex and avoiding needle sharing are some of the preventive measures.
The virus causes Dengue fever. Dengue fever is a flu-like illness spread to human by the bite of infected Aedes aegypti mosquitoes which breed in discarded tires, flower pots, old oil drums and water storage containers close to human dwellings. Dengue mosquitoes bite during the day. Symptoms starts suddenly with a high fever, rash, severe headache, pain behind the eyes and muscle and joint pain. The severity of the joint pain has given dengue the name “breakbone fever”. No antiviral therapy but persons with dengue fever should rest and drink plenty of fluids. Red blood cell and platelet transfusions and fresh plasma are indicated for severe bleeding. No Vaccine to prevent, however we should eliminate mosquito breeding sites in areas where dengue might occur.
Coronaviruses are a group of viruses that include SARS-CoV (Severe Acute Respiratory Syndrome), MERS-CoV (Middle East Respiratory Syndrome) and COVID-19 (Coronavirus disease). COVID-19 is a new strain that was discovered recently in 2019 and has not been previously identified in humans. Coronaviruses are zoonotic, meaning they are transmitted between animals and people. The primary route of transmission is through respiratory droplets, spread via sneezing and coughing. The virus appears to cause more severe disease in older people, people with chronic diseases such as cancer, chronic lung disease, diabetes, renal failure and immunocompromised persons. The clinical spectrum ranges from asymptomatic or mild respiratory symptoms to severe acute respiratory disease, pneumonia and death. Symptoms include fever, cough and shortness of breath. No antiviral therapy and no vaccination is available so far. Standard recommendations to prevent infection spread include regular hand washing, covering mouth and nose when coughing and sneezing. Avoid close contact with anyone showing symptoms of respiratory illness such as coughing and sneezing.
Hepatitis B virus
The virus is transmitted perinatally by infected mothers, sexually, percutaneously (IV drug use), and via mucosal exposure to infectious blood, blood products, or other body fluids. Hepatitis B virus causes acute viral hepatitis, that starts with general ill-health, loss of appetite, nausea, vomiting, body aches, mild fever and dark urine and then progresses to development of jaundice. Complications of its infection include fulminant hepatic failure, chronic hepatitis, cirrhosis and hepatocellular carcinoma. Hepatitis B is treated with antiviral drugs and is preventable with vaccination.
The virus is transmitted via the fecal-oral route and through contaminated food and water. Poliovirus causes polio (poliomyelitis) which mainly affects young children. Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. In a small proportion of cases, the disease causes paralysis, which is often permanent. No antiviral therapy. Supportive treatments such as bed rest, pain control, good nutrition and physical therapy to prevent deformities from occurring over time can help reduce the long-term symptoms due to muscle loss. Polio is preventable by vaccination. `
The virus causes Rabies which infects domestic and wild animals and is spread to people through close contact with infected saliva via bites or scratches. Worldwide, transmission from dogs accounts for >90% of human cases. Initially, non-specific symptoms such as fever, sore throat, malaise, headache, nausea and vomiting occurs. There may be discomfort or a prickling or itching sensation at the site of bite, progressing within days to symptoms of cerebral dysfunction, anxiety, confusion, agitation. As the disease progresses, the person may experience delirium, abnormal behavior, hallucinations, and insomnia. Hydrophobia and aerophobia are cardinal signs but not specific and are unique to humans. Antiviral treatment is not effective. Post-exposure prevention consists of local treatment of the wound and administration of rabies immunoglobulin. Rabies is preventable by vaccination.
The virus is transmitted from person to person through contact with respiratory secretions such as saliva from an infected person. It causes Mumps and symptoms include swollen and tender salivary or parotid glands, difficulty chewing, fever, headache, muscle aches and loss of appetite. No antiviral therapy, the treatment of mumps is supportive. Warm saltwater gargles, soft foods, and extra fluids may also help relieve symptoms. Mumps is preventable by vaccination.
The virus usually spreads through the air via coughs of those who are infected. It causes Measles which is a very contagious respiratory infection. Initial symptoms typically include fever, cough, runny nose and inflamed eyes. Small white spots known as Koplik’s spots may form inside the mouth. A red, flat rash usually starts on the face and then spreads to the rest of the body. No antiviral therapy, the treatment of measles is supportive. Measles is preventable by vaccination.
The virus usually spread through the air via coughs of those who are infected. It causes Rubella, also known as German measles or three-day measles. A rash may start on the face and spreads to the rest of the body. Fever, sore throat and fatigue may also occur. No antiviral therapy, the treatment of rubella is supportive. Rubella is preventable by vaccination.
The virus is transmitted by fecal-oral route and possibly by contaminated surfaces and hands. It causes viral gastroenteritis, with acute onset of vomiting & diarrhoea which lasts from 4-7 days. It is most prevalent in children < 2 years of age. No antiviral therapy, the treatment of rotavirus infection consists of rehydration therapy, fluid & salt replacement – orally / intravenously. Rotavirus infection is preventable by vaccination.
Includes the human viruses variola (smallpox) and molluscum contagiosum. It is spread through respiratory transmission. Molluscum contagiosum and the other poxviruses are acquired through direct contact with lesions. Diseases caused by pox virus are: variola (smallpox), vaccinia, cowpox, monkeypox, molluscum contagiosum. Clinical symptoms are mainly fever, malaise, macules, papules and pustules. Smallpox is the only infectious disease to have been eradicated from world by vaccination.
The virus enters our body through respiratory or fecal-oral route. Adenoviruses most commonly cause respiratory illness; they may also cause gastroenteritis, conjunctivitis, cystitis (bladder infection) and rash illness. Young infants and immunocompromised patients are more susceptible to severe complications of adenovirus infection. No antiviral therapy and no vaccination is available so far.
The virus usually causes infections in animals but Parvovirus B19 infects only human. Parvovirus B19 spreads through respiratory secretions such as saliva, sputum or nasal mucus, when an infected person coughs or sneezes. It can infect children and causes the classic “slapped-cheek” rash of erythema infectiosum (fifth disease). The virus is highly infectious and spreads mainly through respiratory droplets. No antiviral therapy, the treatment of parvovirus infection is supportive and no vaccination is available so far.
The virus spreads via direct contact between humans (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids. Symptoms include sudden fever, weakness, muscle pain, headache and sore throat, followed by vomiting, diarrhea, rash, limited kidney and liver functions, and both internal and external bleeding. Early supportive care and symptomatic treatment improves survival. No antiviral therapy and no vaccination is available so far.
Name originated from ‘Sungai Nipah’; a village in the Malaysian Peninsula. The virus transfers through direct contact with infected bats, infected pigs or from other NiV infected people. Symptoms include fever, headache, drowsiness, disorientation and mental confusion, encephalitis. No antiviral therapy, the treatment of nipah virus infection is supportive and no vaccination is available so far.