MG- Diseases and the disease record

What is a disease?

• 'An alteration of living cels or tissues, that jeopardizes survival in their environment' - Jacques May

Three main catagories

• 1. Infectious conditions (caused by viruses, bacteria, protozoa, rickettsiae and helminths)
• 2. Degenerative and chronic conditions - cancers, cardiovascular and cerebrovascular disease etc.
• 3. Inherited conditions resulting from chromosomal abnormalities - haemophilia etc.

Viruses

• Smallest of life forms, but range quite considerably in size and shape
• Different viruses operate in different ways

Early mortality data: Sources and Difficulties of interpretation

• Early mortality data refers to data before wold war 2
• 1532 - mandated that London parish priests compile weekly "Bills of mortality" which are the primary source of the first known life table
• By the end of the 19th century civil registration was compulsory in virtually all European countries
• The decennial U.S Censuses of Mortality are the main source of nationwide mortality data from 1850 to 1890, but they are seriously incomplete. In constrast to the situation in the uk where civil registration data, including cause of death and limited socio-economic data, are quite accurate from the mid-nineteenth century forward
• Statistics collected and special studied prepared by life insurance companies represent an underutilized body of data for nineteenth century mortality in the United States and Europe - Because of the financial incentive to maintain accurate death records these might be quite accurate and contain cause of death detail
• Problems? Definitions of death e.g. still births?
• Misallocation of deaths by place of occurence
• Age misreporting

The meaning of the term disease surveillance has changed over the last 100 years

• Continuous monitoring of a diseased patient – Before 2^nd World War
• Monitoring disease in an entire country – After 2^nd  World War

Iceberg concept of infection:

• Top of iceberg – death of human being
• Clinical disease of manifestation (visible)
• Subclinical disease – patient is unaware of the disease
• At bottom is exposure to disease without infection

Fundamental distinction between the recorded levels of illness or injury and the actual levels of illness or injury

Reason a case might be lost to surveillance:

• If a patient is unaware that they have a disease
• If the patient is diagnosed incorrectly
• If the disease is not currently under surveillance

If a doctor does not catalogue a disease in the notifiable disease list then they may receive a fine or even prison

Disease data: interpretive problems

·      Disease classification and definitions

Different definitions of diseases in different countries, meaning that some disease cases are not being recorded

·      Non-reporting/Under reporting

·      Reporting delays

W.H.O. reports of HIV in Brazil only showing a fraction of actually cases

·      Population Mobility

Problem of where the case should be reported as originating. Many people will travel to different parts of the country for treatment.

·      Boundary Changes

Boundaries of health districts change over time making the cataloguing of cases in different locations difficult

All these problems can cause disease surveillance data to become very unreliable

• 1532 – key date in disease record – mandated that priests in London to compile weekly list of deaths in their respective parishes.
• 1603- start of regular publication of Bills of mortality. 

US International disease archive 1887-1912

• 1741: Rhode Island: reporting of contagious diseases by tavern keepers
• Increase in shipping in the US – this may be the reason why there were increases in disease cases (sharp rise in the 1880s)
• Not uncommon for people to die on board ships going to USA
• 200 towns/cities surveyed 
• Although in many areas the government didn't release the mortality data so the consules had to draw the information from gravediggers and doctors
• Competance and dedication could be questioned

Limitation

• Completeness of the reporting system (war, famine and extreme weather event could stop reports)
• Quality of diagnosis
• Definition of reporting units (city boundries changing) 

The importance of long term public health records in public health surveillance: the US weekly sanitary reports 1888-1912, revisited

History of the US public health records

• 1741 - the colony of Rhode Island passed an act requiring tavern keepers to report contagious diseases amoung their patrons
• 1925 - All states participating in national morbility reporting. As the 19th century progressed, the number of vessels heading for the US increased - Six statutes were passed between 1850 and 1880 that authorized both the quarantine of vessels and the measures to be taken for the prevention of epidemics
• John M.Woodworth - In the wake of the 1873 cholera epidemic an international disease surveillance system was advanced to stop diseases entering the country. US consuls were scattered around the world and were to submit weekly summories of mortality in there jurisdictions (The 1878 Quarantine Act)
• Representitves did not always have medical expertise
• 1893-National Quarantine authorized the detail of medical officers to US consulates overseas - based mainly in port cities to assist with ship and passenger inspection.

• "The foreign city mortality tables contain weekly mortality information for up to 11 diseases, and all causes, for some 250 consular cities"
• In 100 of these cities, reporting is complete and so they contain relatively complete series for mortality from 6 diseases (diptheria, measles, scarlet fever, tuberculosis, typhoid and whooping cough)
• Data is for selected cities and not for the country as a whole
• Many weekly reports have been lost
• Delay in reporting for up to 6 weeks was not uncommon and in some reports it was unknown which week it was refering to.
• Data had to be assembled into machine readable form
• The reports make occational references to data supplied by coffin manufacturers, grave diggers and other unofficial sources.
• Many places in the tables were growing rapidly in the late 19th century 'real city' vs 'legal city'
• These reports may help health officials predict the future health problems of developing third world countries
• International data at the world level only become available with the setting up of the League of Nations Health Section in 1923; the weekly consular reports allow the international perspective to be extended back by several decades.

Deciphering Global Epidemics: Analytical Approaches to the Disease Records of World Cities, 1888-1912.

• Over the last 100 years there has been a spectacular fall in mortality from the classic infectious diseases, due to the increase in vaccines and antibiotics
• As late as 1970, W.H.Stewart, the then surgeon general, told the United States congress that it was time to close the book on infectious diseases, declare the war against pestilence won, and shift national resources to such chronic problems as cancer and heart disease.
• But, within the decade, a new pandemic disease, AIDS, was emerging that seemed likely to kill in the next two decades as many victims as small pox in all previous years of the twentieth century.
• Recognition of new infectious diseases such as Ebola and Lyme
• Epidemic: Unusually high incidence of a disease/in excess of expectancy