Emerging Viruses

Emerging Viruses

Introduction to emerging viruses
A virus is an infectious agent that is incapable to grow or reproduce outside a host cell. It itself can cause severe problems with health and even lead to death in a long term or short term period whereby it reproduces itself inside a human body.
With a slight knowledge on the effects of what virus area capable of, we would like to talk about new viruses or evolution of the viruses, in other words, Emerging virus.
The factor that contribute to emerging viruses are usually mutation of the virus which we would term it Spontaneous evolution of virus.

• Many viruses, in particular RNA viruses, have short generation times and relatively high mutation rates.
• This elevated mutation rate, when combined with natural selection, allows viruses to quickly adapt to changes in their host environment.

For example, a series of outbreaks of virus within the 6 years are as follows;

Year 1999 ( West Nile Virus)
West Nile virus is an emerging virus that first appeared in North America during the summer of 1999 in New York City. There were seven deaths associated with this event. Surveillance reports indicate that the virus had been spreading south and west and in 2002, had been reported in 42 states and the District of Columbia. As of September 2002, there were 2121 total human cases reported, inducing 104 deaths. The fatality rate for the West Nile virus is very low and the majority of individuals will have no clinical symptoms; however, individuals at most risk for more serious form of the disease are the elderly, the immunocompromised, and young individuals. The virus is spread by certain mosquito species and certain populations of birds serve as the reservoir hosts. Because person-to-person transmission does not occur, humans are therefore considered dead-end hosts. Confirmation of cases West Nile virus infections in humans are determined based on clinical and laboratory findings.

September 1998 – April 1999 (Nipah Virus Outbreak)
Nipah virus is a newly recognized zoonotic virus. The virus was 'discovered' in 1999. It has caused disease in animals and in humans, through contact with infectious animals. The virus is named after the location where it was first detected in Malaysia. Nipah is closely related to another newly recognized zoonotic virus (1994), called Hendra virus, named after the town where it first appeared in Australia. Both Nipah and Hendra are members of the virus family Paramyxoviridae. Although members of this group of viruses have only caused a few focal outbreaks, the biologic property of these viruses to infect a wide range of hosts and to produce a disease causing significant mortality in humans has made this emerging viral infection a public health concern.

Nipah Virus

Nipah Virus

November 2002 – July 2003 (SARS Outbreak)
Severe acute respiratory syndrome (SARS) is a respiratory disease in humans which is caused by the SARS corona virus. There has been one near pandemic to date, between November 2002 and July 2003, with 8,096 known infected cases and 774 deaths worldwide being listed in the World Health Organization's (WHO) 21 April 2004 concluding report. Within a matter of weeks in early 2003, SARS spread from the Guangdong province of China to rapidly infect individuals in some 37 countries around the world. Mortality by age group as of 8 May 2003 is below 1 percent for people aged 24 or younger, 6 percent for those 25 to 44, 15 percent in those 45 to 64 and more than 50 percent for those over 65. For comparison, the case fatality rate for influenza is usually around 0.6 percent but can rise as high as 33 percent in locally severe epidemics of new strains. The mortality rate of the primary viral pneumonia form is about 70 percent.

SAR Virus

Year 2008 (Avian Influenza virus)
Avian influenza, also known as bird flu, is caused by avian influenza virus, which belongs to the family Orthomyxoviridae, and affects most domestic and wild bird species. The influenza viruses are divided on the axiom of their antigenic nature into types A, B and C. Only type A influenza viruses are of diversion to veterinarians, whereas types B and C are usually found in humans. Avian influenza viruses are further sorted by their surface proteins, haemagglutinin and neuraminidase. There are 15 different haemagglutinin (H1-15) and nine neuraminidase (N1-9) subtypes based on serological testing with the haemagglutinin-inhibition and neuraminidase inhibition tests, respectively. The virulence of the avian influenza viruses varies broadly from very low to very high and signs of disease range from mild respiratory to viscera-tropic, multi-systemic infections with catastrophic consequences. Low pathogencity avian influenza (LPAI) viruses can be any of the 15 haemagglutinin and nine neuraminidase subtypes, whereas highly pathogenic avian influenza (HPAI) viruses have only been of the H5 and H7 haemagglutinin subtypes. Generally, antibodies against one of the haemagglutinins offer little or no protection against a virus with a different haemagglutinin subtype.
The virus remains viable for long periods in tissues and faeces. Various physical and chemical treatments can inactivate the virus, such as temperatures of 56°C for 3 hours or 60°C for 30 min, acidic pH, oxidizing agents, sodium dodecyl sulphate, lipid solvents, ß-propiolactone, as well as formalin and iodine disinfectants.

Reference

http://www.lapublichealth.org/
http://microbiology.mtsinai.on.ca/bug/wnv/bug-images/wnv_cycle.jpg
http://www.ncbi.nlm.nih.gov/
http://bepast.org/docs/photos/nipah%20virus/nipah%20virus.jpg
http://www.wpro.who.int/
www.influenzareport.com/ir/ai.htm
http://en.wikipedia.org/wiki/Virus
http://en.wikipedia.org/wiki/West_Nile_Virus
http://en.wikipedia.org/wiki/SARS
http://en.wikipedia.org/wiki/Nipah_Virus
http://en.wikipedia.org/wiki/Avian_Flu