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Morbidity Rates

Morbidity Rates. Ashry Gad Mohamed Professor of Epidemiology. Incidence. It measures the new cases. It measures the force of infection or disease in the community. IR= No. of new cases during a year / lacality X 10 n Population at risk /year/locality. Example

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Morbidity Rates

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  1. Morbidity Rates Ashry Gad Mohamed Professor of Epidemiology

  2. Incidence • It measures the new cases. • It measures the force of infection or disease in the community. • IR= No. of new cases during a year / lacality X 10n Population at risk /year/locality

  3. Example • In 1426 the number of breast cancer cases reported to the cancer registry in Riyadh region was 200. The midyear population of Riyadh region was four million. Calculate the incidence of breast cancer in Riyadh.

  4. Attack rate • Acute recurrent diseases e.g. ARTI, food poisoning. • Person may catch the disease more than one time. No. of episodes during specified period • AR= x k Population at risk/ period

  5. Example: • In a village of 600 persons, 1200 visits to the PHCC were due to flu. What is the attack rate of flue in the village?

  6. Factors affect incidence 1- New risk facor Contraceptive pills & thromboembolism. Food additives & cancer New agent HIV & AIDS

  7. 2- Changing virulence El-Tor vibrio & cholera. Influenza virus mutation & influenza Mycobacteial resistance & TB

  8. 3- Changing pattern of intervention • Polio eradication & poliomyelitis • Chemoprophylaxis & meningitis • Environmental sanitation & filth diseases

  9. 4-Population pattern • Aging & degenerative diseases & cancer

  10. 5- Reporting • Increase in reporting & incidence • Early stage of surveillance & incidence

  11. 6-Screening Screening early detection of cases Increase in incidence

  12. 7-New diagnostics New diagnostic Increase detection of cases Increase in incidence

  13. 8-Selective migration Floods or famines Decrease sanitation Increase susceptable Increase incidence

  14. Prevalence • It measures the status of the disease in the population. • Point prevalence: Total cases (old + new) at fixed point of time in place x 10 n total population in the place

  15. Period prevalence Total cases (old + new) during a period of time in place x 10 n total population in the place

  16. example • MOH conducted a survey for RVF among workers in slaughterhouses in Makkah. 224 seropositive workers were identified among 6000 workers. • Calculate the prevalence of RVF.

  17. Factors affecting prevalence 1- Incidence Prevalence = incidence X duration 2- Disease duration Chronic diseases are accumulating so increase the prevalence

  18. 3- management programs • If successful and curative decrease the prevalence. • If only increases the survival without complete cure increases the prevalence

  19. 4- Changing classification • Blood pressure 140/80 Vs 160/90 Fasting blood sugar 126 Vs 140

  20. 5-Selective attrition • If cases of the disease travel to be treated abroad then the prevalence decreases.

  21. Incidence Vs prevalence incidence Prevalence Cure Death Migration

  22. P No. I Time

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