Epidemiology and Control of Communicable Diseases

Question: Discuss about the Epidemiology and Control of Communicable Diseases. Answer: Introduction: Staphylococcus aureus can live on skin for the longer period and they also prefer to live in warmest, darkest place such as the nose. Mostly nasal colonization takes place and host respond to this by expression of anti-microbial peptides and cytokines. In this condition both the patients are described as colonized (4). In IV drug user, injection drug is one of the major sources of HIV infection as people can get HIV from sharing drug preparation or injecting equipments. Shared needle is basically the main cause of infection because as it contains contaminated blood of infected persons and peripheral blood, lymphoid tissue and bone marrow is the main reservoir for infection. IV drug users take injected drugs that are introduced into the bloodstream using needle and syringe. HIV infected blood can get into blood stream at the time of preparation of drug using blood contaminated syringes, reusing bottles to dissolve drugs into water and reusing cottons to filter out things that block the needles (9). Immunogenicity is indirectly related to transmissibility in an endemic area. Immunogenicity is the ability of the human body immune system to induce adaptive and humoral cell immune response in response to entry of an antigen. It is a means to check transmissibility of infection by provoking an immune action against the infection. It leads to immunologic memory. Therapeutic agents like proteins leads to hypersensitive reaction and formation of antibodies against the protein. The level of immune status and genetic factor has impact on immunogenicity. Thus immunogenicity is a factor that indirectly minimizes the transmissibility of disease or infection (8). Infectious agents such as protozoa, bacterium or virus changes surface proteins in order to evade immune response of host. This kind of antigenic variation in an organism is a mechanism to target specific host, repeatedly infect single host and quickly transmit to host cells. It is a response by organism to fight against immunogenicity of host cells. It is an approach to immune evasion by pathogen and reinfecting host as antigen is not recognized by immune system. It also has an impact on the duration of parasite infection within a host cell. Antigenic variation provides host cell with immune memory (6). Polio epidemic was first encountered in the nineteenth century. At that time all children were exposed with the polio virus and protected by maternal antibodies. With change in times and improved environmental hygiene and sanitation, age at which people are diagnosed with polio significantly increased. Children encountered the virus at an increased age compared to previous polio cases in children and they were no longer protected by maternal antibody (3). Before development in sanitation, children became exposed to the virus but exposure provided them with permanent immunity to the virus. But with modern ideas in hygiene, children are not exposed the virus in infancy and they do not develop natural immunity against it. The ultimate result is that severe symptoms of disease began to be seen. Now there are relatively fewer cases in young children and increase in number of young adults affected by it (2). If a person contracts polio infection, symptoms appear within 5-35 days. The subclinical infection of polio is associated with headache, fever vomiting and sore throat while clinical infection affects the central nervous system. Symptoms of clinical infection include back pain, skin rash, fever, difficulty in breathing, muscle spasm, etc. 90% of polio infection is subclinical type of infection. Polio infection aggravates due to environmental sources of infection like contaminated water, food, flies and poor sanitation. With the improvement in environmental sanitation and hygiene, enteric infection will get delayed and it will reduce the clinical: subclinical ratio of polio cases in endemic area (11). Hepatitis A virus infection is transmitted through ingestion of contaminated water, food or direct contact with infectious person. In order to give advice to Community Aid abroad to prevent infection, it will be necessary know about overseas environmental factors like availability of safe water, food safety procedures and level of sanitation and hygiene in the country. Countries with poor sanitary condition and hygiene practice have been found to have more number of cases of Hepatitis A infection (6). In CAA workers it is necessary to know about their sanitary habits, their living conditions and the kind of foods they consume. It is important because often people living lesser developed areas have more chance of infection. Poor and low quality food also has chance of Hepatitis A infection, so knowing this factors about CAA workers will be necessary. Gonorrhea is caused by gram negative agent diplococcus, Neisseria gonorrhoeae and the infection occurs in the upper or lower tract, rectum area, cervix, urethra and bloodstream. The bacterium does not survive in the environment and prefers CO2 environment, so urogenital site is the main site for infection. Neiserria gonnorrhoeae is a fragile organism and sensitive environmental factors like temperature change, UV light exposure and drying (7). Sexually active men and women are at high risk of acquiring this kind of infection and transmitting the disease. Vertical transmission also occurs by transfer from mother to child during birth. Once the Neisseria gonorrhoeae enters the mucous membrane of urogenital tracts, they utlize their surface pili to anchor at the infection site and target non-ciliated epithelial cells, The pili prevents the phagocytosis of neutrophils and digests IgA on the surface of urethra and cervix. This is done by IgA protease within the pili and helps in attachment of bacteria to these surfaces. This adherence allows transmission of organism inside the fallopian tube and initiates the mechanism of infection. The gonococci replicates after adherence to non-ciliated cells where they are exocytosed into subepithelial cells and inflammations and other symptoms occur. Socioenvironemtal factors like practices of sex and use of safe practices also affects the transmission of the disease (8). Gonorrhea and Chlamydia can be prevented or treated with antibiotic given to patients orally or by injection. Antibiotic treatment disrupts the chain of transmission of bacterium and prevents the infection from getting worse. Generally combination of dual antibiotics like cephalosporin and azithromycin is used to improve efficacy of treatment. Ciprofloxacin also used in treating sexually transmitted disease (5). Other methods for controlling infections include using antiviral medication or dug combination therapy. The methods for prevention will include health education to provide information about sexual health and interventions to promote sexual health The recent sharp increase of gonorrhea from 1400 per 100,000 population in 1999 to 2225 in per 100,000 population in 2009 indicate a possible decline in safe sex practice which increase the gonorrhea transmission. The other factor is the decreased sensitivity of N. gonorrhoea to antimicrobial drugs (10). Culture and sensitivity Positive Negative Total Urinary PCR Positive 750 150 900 Negative 50 9050 9100 800 9200 10000 Sensitivity Specificity Positive predictive value Negative predictive value Culture and sensitivity 8% 7.5% 93.75% 98.36% Urinary PCR 9% 7.5% 83.33% 100% The symptoms of gonorrhea are mostly asymptomatic in both men and women. As gonnorhea is asymptomatic, screening is critical for identification and prevention of upper genital tract infection and preventing all forns of transmission. The gonnorhea surveillance will involve widespread routine genital screening to assess risk for infection among women. Women are at more risk due to multiple sex partners, inconsistent condom use and HIV infection associated with sexual activity. Pharyngeal screening is also essential for identification of those women who were missed with traditional genital tract screening (4). Due to asymptomatic characteristics of the disease, widespread screening is essential to identify people who are at risk of the disease. Specific testing for gonorrhea because of apparent notification rate in males and females. Yes, this is also the case for indigenous community because they have limited access to sexual health service and so surveillance will be of utmost importance HIV is an example for sensitive case definition because the disease is widespread and it is necessary to have a sensitive case definition. Tuberculosis because it requires standard case definition and controlling disease because treatment protocols are not well-defined. References: Andric B, Drowos J, Trepka MJ, Suciu G, Alonso A, Hennekens CH. High frequencies of negative pretreatment results following presumptive antibiotic treatment for chlamydia and gonorrhea. Southern medical journal. 2013 May;106(5):321-6. Closser S, Cox K, Parris TM, Landis RM, Justice J, Gopinath R, Maes K, Amaha HB, Mohammed IZ, Dukku AM, Omidian PA. The impact of polio eradication on routine immunization and primary health care: a mixed-methods study. Journal of Infectious Diseases. 2014 Apr 1:jit232. Polio and Sanitation: Inside Vaccines [Internet]. Insidevaccines.com. 2010 [cited 21 September 2016]. Available from: https://insidevaccines.com/wordpress/2010/07/01/polio-and-sanitation/ Danielsson-Tham ML. Staphylococcal Food Poisoning. Food Associated Pathogens. 2013 Sep 25:250. (1.1) Fagan PS, Downing SG, McCall BJ, Carroll HJ, Howard TM, Palmer CM. Enhanced surveillance for gonorrhoea in two diverse settings in Queensland in the 2000s: comparative epidemiology and selected management outcomes This paper analyses enhanced surveillance data for gonorrhoea from an urban and a remote region of Queensland during the 2000s. It describes the diverse epidemiology of this condition in these two populations and details management challenges and outcomes. Page last updated: 21 February 2014. (3.5a)Frank S. Benefits of Antigenic Variation. Princeton University Press [Internet]. 2002 [cited 19 September 2016];. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2405/ Hlady RA, Tiedemann RL, Puszyk W, Zendejas I, Roberts LR, Choi JH, Liu C, Robertson KD. Epigenetic signatures of alcohol abuse and hepatitis infection during human hepatocarcinogenesis. Oncotarget. 2014 Oct 15;5(19):9425. (2.2) Pathogenic Neisseriae: gonorrhea and meningitis [Internet]. Textbookofbacteriology.net. 2016 [cited 21 September 2016]. Available from: https://textbookofbacteriology.net/neisseria.html Leone PA, Hynes NA, McGovern BH. Epidemiology, pathogenesis and clinical manifestations of Neisseria gonorrhoeae infection. UpToDate.[Online][Cited: February 18, 2014.] https://www. uptodate. com/contents/epidemiologypathogenesis-and-clinical-manifestations-of-neisseria-gonorrhoeae-infection. 2013. (3.1) Metcalf CJ, Ferrari M, Graham AL, Grenfell BT. Understanding Herd Immunity. Trends in immunology. 2015 Dec 31;36(12):753-5. (1.4) Westergaard RP, Hess T, Astemborski J, Mehta SH, Kirk GD. Longitudinal changes in engagement in care and viral suppression for HIV-infected injection drug users. AIDS (London, England). 2013 Oct 23;27(16):2559. (1.2) On AY, Sungur U. Patients with post-polio syndrome are more likely to have subclinical involvement as compared to polio survivors without new symptoms. Annals of Indian Academy of Neurology. 2016 Jan;19(1):44.