Sunday, August 1, 2010

62 - Small Pox

*Small is an acute infectious disease caused by VARIOLA VIRUS and clinically characterized by a sudden onset of fever, headache, backache, vomiting and sometimes convulsions, especially in children.

*On the third day of fever, a typical rash appears which is centrifugal in distribution and passes through successive stages of macule, papule, vesicle, pustule and scab with subsequent scarring.

- May 17, 1975 = The last indigenous case of small pox occured in India (Bihar).
- May 24, 1975 = India's last known case of small pox, an importation from Bangladesh occured.
- July 5, 1975 = India was proclaimed as no longer to be small pox endemic.
- October 26, 1977 = World's last case of Small pox occured in Somalia.
- 1978 - Lab accident results in small pox.
- May 8, 1980 = WHO declared that small pox has been eradicated completely.

*Epidemiological factors which have led to the eradication of small pox - these could form the basis for the eradication of other similar diseases :
1. No long-term carrier of the virus
2. No known animal reservoir
3. Life-long immunity after recovery from the disease
4. The detection of cases comparatively simple because the rash was so characteristic and occured in visible parts of the body
5. Persons with sub-clinical infection didnot transmit the disease
6. Vaccine is highly effective; easily administered, heat stable and confers long-term protection.
7. International co-operation.

*As small pox is now eradicated it is often asked, why keep the causative agent and take the risk of laboratory-associated infection? The answer lies in the fact that there exists, in various parts of the world, a number of poxviruses (eg: monkeypox, cowpox, camelpox, tanapox, tateropox) that closely resemble smallpox viurs and can producehuman infections. Other new pox viruses may yet be discovered . The natural histories of these viruses have not yet been delineated, and it is not known whether these agents can someday replace the eradicated smallpox virus. It is necessary to conduct comparative studies on these animal poxviruses.

*To protect from future attacks, vaccine stocks and bifurcated needles for vaccination of about 300 million people are maintained indefinitely by WHO in Geneva, Toronto and New Delhi.

Monday, March 1, 2010

61 - Cold chain and Reverse Cold chain

The 'cold chain' is a system of storing and transporting vaccines at recommended temperatures from the point of manufacture to the point of use. That is, the role of the cold chain is to maintain the potency of vaccines. There is also a concept called 'reverse cold chain', which is a system of storing and transporting samples at recommended temperatures from the point of collection to the laboratory.

Essential elements:

*Personnel to manage vaccine distribution
*Equipment for vaccine storage & transport
*Maintenance of equipment

The equipment included in the so-called 'cold chain' is expected to provide 'EPI standard' vaccine storage. The capacity needs to provide for transport and storage of all vaccines required for routine immunization of all children under 1 years of age (4%) and all women of childbearing age, groups that constitute 4% and 23% of the total population in Ethiopia, respectively. The cold chain is also expected to provide for the needs related to various supplementary immunisation activities at any given time.

In August/September 2002, the Ministry of Health in collaboration with the World Health Organization, carried out a national inventory exercise in Ethiopia. The inventory was analysed mid-2003 and the following is a summary of the findings:

1.Only 66% of the cold chain equipment was found functional at the time of the inventory. Excluding 3% of the equipment for which no record was available, 31% of the equipment was therefore not available to support immunization activities.
2.Of the 31% non-functional equipment, over 600 units were reportedly awaiting spare parts and repair work.
3.Of the non-functional units, 522 are over 10 years of age, thus making them uneconomical to repair. The average lifespan of EPI cold chain equipment is 7 to 10 years depending on environment and use.
4. 51 different manufacturers account for the 4,833 equipment inventoried - a situation that makes it difficult to maintain adequate spare part stock for maintenance.

Three key observations/recommendations are included at the end of the report, based on analysis of the inventory and technical considerations. They revolve around three key issues established in the report; the need for:

1.Standardization of equipment,
2.Development of a five-year rehabilitation plan and,
3.Establishment of sustainable equipment maintenance system and guidelines.

The three recommendations have been incorporated into the WHO/EPI Logistics work plan for 2004 with intention to address them in collaboration with the Ministry of Health over the next five years. In addition, a four-week training of 35 regional cold chain technicians has recently been conducted by the Ethiopian Science and Technology Commission (ESTC) on behalf of the Ministry of Health in collaboration with UNICEF and WHO. This training is expected to further enhance the capacity of the regions to independently run effective maintenance of their cold chain equipment.

Multiple Choice Questions in Epidemiology and Community Medicine (Revision MCQs)

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