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Friday, January 29, 2010 @ 6:30 PM
Entry05: Emerging Viruses Emerging Viruses Introduction: Emerging virus are viruses that has newly appeared in a human population and is rapidly increasing in disease incidence. The virus has adapted and emerged as a new disease or pathogenic strain, with attributes facilitating pathogenicity in a field not normally associated with the original virus. This includes viruses that are the cause of diseases which has notably increased in incidence; this is often a result of a wide variety of causes from both the influence of man and nature. Most emergent viruses can be categorized as zoonotic (an animal disease that can be transmitted to humans), this has the advantage of possibly having several natural reservoirs for the disease. Reason for Emergence There are 2 main factors as to why for the emergence, they are Virus Factors & Human Factors. Under Virus factor: 1. Spontaneous evolution of new virus entity 2. Generation of a novel strain due to co-infection of different strains in an individual(random assortment) Viral population is heterogenous which mean it can only be derived from a different individual or species and viral have high mutation rates due to selection pressure. Random assortment which only happens in virus with segmented genome is where Lego blocks of 2 different viruses, after penetrating the cell membrane; it dissembles and reassembles randomly which cause co-infection of both virus. The Viruses next replicate inside the host, RNA strands are being transcribed thus synthesis of new viral proteins and the new virus is produced. New virus particles are release. Click here for image All together, there are a total of 16 different H - Hemagglutinin types & 9 different N – Neuraminidase types, e.g H1N1, H3N2 , etc. however there are only 4 strains of avian influenza virus that are known to cause disease in humans. However how many permutation are there actually the answer is still really unknown, in the near future there may appear a new avian influenza breakout. Human Factors: Because of the concentration of population and they many different habit and lifestyle makes is easier for virus break out. For example; the transmission of HIV and Hepatitis C among drug users this due to the sharing of unsterile needles. In undeveloped countries due to poverty there is a lack of education which leads to the lack of knowledge of proper hygiene and personal care thus causing breakdown in public health. e.g. HIV in Africa and china Because of climate changes the temperatures in different region of the world starts to changes .The early effects of global warming have already been observed in different geographical areas. In Europe elevated average temperatures in West-Central Europe have been associated with more frequent Puumala hantavirus outbreaks, through high seed production (mast year) and high bank vole densities. On the other hand, warm winters in Scandinavia have led to a decline in vole populations as a result of the missing protective snow cover. Additional effects can be caused by increased intensity and frequency of extreme climatic events, or by changes in human behaviour leading to higher risk of human virus exposure. Regardless of the extent of climate change, it is difficult to predict the impact on hantavirus survival, emergence and epidemiology. Nevertheless, hantaviruses will undoubtedly remain a significant public health threat for several decades to come. Man invading natural habitat of animal Due to population pressure human are forces into new areas where potentially virulent viruses may be lurking. More land is needed for example agricultural thus bring human closer to the wild animals. Virus on infected wild animals may jumped to humans as a result causing new virus to form , which lead to the increase possibility of zoonoses. Here are some examples of emerging viruses over last 10 years! H1N1 virus Swine influenza (also know as swine flu) is an infection by any one of several types of swine influenza virus. Swine influenza virus is any strain of the influenza family of viruses that is endemic in pigs. A subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3. Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. The meat of an infected animal poses no risk of infection when properly cooked. Dengue Dengue The incubation period is 3-15 days; most common is 5-6 days. Classic Dengue has symptoms of fever, chilly sensation, severe headache, nausea, severe bone and joint pain. Dengue Hemmorrhagic Fever has the same symptoms as the classic form, also with internal bleeding and shock. If the patient survives the infection, it causes a sensitization instead of immunization. Classic Dengue virus infects approximately 1 million people per year; 15% of the infections progress into Dengue Hemorrhagic Fever. It is an arbovirus that is transmitted by Aedes Aegypti. All infections are from a mosquito vector. SARS Severe acute respiratory syndrome (SARS) is a new viral respiratory illness first identified in humans in early 2003. The SARS virus spreads primarily by close human contact, either through the air or by touching a contaminated surface. The time between exposure to the SARS virus and the onset of symptoms of SARS is called the incubation period. The incubation period for SARS is typically two to seven days, although in some cases, it may be as long as 10 days. Symptoms of SARS usually begin with a high fever, marked by a temperature greater than 100.4°F (38.0°C). Other early SARS symptoms may include: • Headache • An overall feeling of discomfort • Body aches • Chills. However in some patients, body aches and headaches may appear 12 to 24 hours before fever. Some people may also have mild respiratory symptoms such as sore throat or runny nose at the outset. About 10 to 20 percent of patients with symptoms of SARS have diarrhea. After two to seven days, SARS patients may develop a dry cough and shortness of breath. These SARS symptoms may be accompanied by or progress to a condition in which the oxygen levels in the blood are low (hypoxia). In 10 to 20 percent of cases, patients require mechanical ventilation and most patients develop pneumonia. Labels: #entry |
