2.2 Aetiological Agent: Classification And Characterisation
2.2 Aetiological agent: Classification and characterisation
The monkeypox virus is a member of the genus orthopox (family Poxviridae). Other members include cowpox, vaccinia, and variola (smallpox) viruses. Poxviruses are the largest vertebrate viruses known. The virions contain a linear double-stranded deoxyribonucleic acid (DNA) genome and enzymes that synthesise messenger ribonucleic acid (RNA). The viruses multiply in the cytoplasm of the host cells. The poxvirus family consists of two subfamilies, namely: the Chordopoxvirinae and the Entomopoxvirinae.
The Chordopoxvirinae consisting of eight genera. Members of a genus are genetically and antigenetically related. The genus Orthopoxvirus comprises camelpox, cowpox, ectromelia, …show more content…
On the basis of genome studies, there is also strong evidence that monkeypox is not ancestral to variola virus. This may be important in view of the fear expressed by some that variola might evolve from monkeypox. In the pre-molecular era, great efforts were made to distinguish the four viruses by serological reactions. These were delicate studies since the viruses share most antigens (Gispen and Brand-Saathof, 1974). Some results were obtained through the use of absorbed sera in agar gel diffusion tests, but these were rapidly superseded by the study of the biological characteristics and DNA restriction patterns, the latter being used exclusively at present. The development of relatively specific antigens has been extremely useful for serological surveys in man and animals. In the field, rapid presumptive diagnosis of orthopoxvirus infection is necessary, as is differentiation from chickenpox, as confusion is possible on clinical grounds. For this purpose, scabs of the lesions are sent, without transport medium, to the diagnostic laboratory. Electron microscopic examination of this material allows the differentiation of orthopox- and herpesviruses. The poxviruses can be detected in more than 95% of the scabs, whereas varicella-zoster virus is detected in only half of the material from cases of chickenpox, meaning that electron microscopy negative specimens are very unlikely to be …show more content…
Epidemiology
3.1 Occurrence
People living in or near the forested areas may have indirect or low-level exposure, possibly leading to subclinical infection (Reynolds et al., 2010). The disease is rare and only known to be indigenous to the rain forests of western and central Africa. It was first recognized in humans in 1970 after the eradication of smallpox, possibly because of the subsequent unmasking of the infection. Surveillance reports from 1981-1986 documented
338 cases in the DRC (out of a 1982 estimated population of 5 million). In the 1996-1997 outbreaks in the DRC, the attack rate was 22 cases per 1000 population. Human infection with monkey pox has not been reported in West Africa since 1978. However, monkeypox continues to exhibit a robust emergence in the DRC, with sporadic occurrences of disease in neighbouring countries. In 2003, 11 cases and 1 death were reported from the DRC and
10 cases with no deaths were reported from Sudan in 2005 (Reynolds and Damon, 2012). In United States no cases occurred until the late spring 2003 outbreak in the Midwestern states. Between May 16 and June 20, 2003, 71 suspected cases of monkeypox were investigated (CDC., 2013).
3.2
The monkeypox virus is a member of the genus orthopox (family Poxviridae). Other members include cowpox, vaccinia, and variola (smallpox) viruses. Poxviruses are the largest vertebrate viruses known. The virions contain a linear double-stranded deoxyribonucleic acid (DNA) genome and enzymes that synthesise messenger ribonucleic acid (RNA). The viruses multiply in the cytoplasm of the host cells. The poxvirus family consists of two subfamilies, namely: the Chordopoxvirinae and the Entomopoxvirinae.
The Chordopoxvirinae consisting of eight genera. Members of a genus are genetically and antigenetically related. The genus Orthopoxvirus comprises camelpox, cowpox, ectromelia, …show more content…
On the basis of genome studies, there is also strong evidence that monkeypox is not ancestral to variola virus. This may be important in view of the fear expressed by some that variola might evolve from monkeypox. In the pre-molecular era, great efforts were made to distinguish the four viruses by serological reactions. These were delicate studies since the viruses share most antigens (Gispen and Brand-Saathof, 1974). Some results were obtained through the use of absorbed sera in agar gel diffusion tests, but these were rapidly superseded by the study of the biological characteristics and DNA restriction patterns, the latter being used exclusively at present. The development of relatively specific antigens has been extremely useful for serological surveys in man and animals. In the field, rapid presumptive diagnosis of orthopoxvirus infection is necessary, as is differentiation from chickenpox, as confusion is possible on clinical grounds. For this purpose, scabs of the lesions are sent, without transport medium, to the diagnostic laboratory. Electron microscopic examination of this material allows the differentiation of orthopox- and herpesviruses. The poxviruses can be detected in more than 95% of the scabs, whereas varicella-zoster virus is detected in only half of the material from cases of chickenpox, meaning that electron microscopy negative specimens are very unlikely to be …show more content…
Epidemiology
3.1 Occurrence
People living in or near the forested areas may have indirect or low-level exposure, possibly leading to subclinical infection (Reynolds et al., 2010). The disease is rare and only known to be indigenous to the rain forests of western and central Africa. It was first recognized in humans in 1970 after the eradication of smallpox, possibly because of the subsequent unmasking of the infection. Surveillance reports from 1981-1986 documented
338 cases in the DRC (out of a 1982 estimated population of 5 million). In the 1996-1997 outbreaks in the DRC, the attack rate was 22 cases per 1000 population. Human infection with monkey pox has not been reported in West Africa since 1978. However, monkeypox continues to exhibit a robust emergence in the DRC, with sporadic occurrences of disease in neighbouring countries. In 2003, 11 cases and 1 death were reported from the DRC and
10 cases with no deaths were reported from Sudan in 2005 (Reynolds and Damon, 2012). In United States no cases occurred until the late spring 2003 outbreak in the Midwestern states. Between May 16 and June 20, 2003, 71 suspected cases of monkeypox were investigated (CDC., 2013).
3.2