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disease - Coggle Diagram

- - - - they are able to penetrate deep into people's lungs
      - tiny air-borne particles smaller than 2.5 micrometres that are released by burning fossil fuels
    - - they cause serious respiratory problems (asthma, bronchitis) as well as lung and heart disease
      - additionally, pm 2.5 pollution in Delhi has resulted in residents being at a 70% higher risk from lung cancer
    - - the WHO's guidelines set safe pm 2.5 pollution levels at 10 micrograms per cubic metre. India, however, sets permissible levels at 40
      - even so, pm 2.5 levels exceed this in most large cities; in winter months, air pollution in Delhi often exceeds 600 micrograms per cubic metre
  - - - compared with less polluted, rural areas in India, respiratory symptoms and diseases such as asthma are 1.7 times higher in Delhi
      - lung function among Delhi's inhabitants is on average 40% reduced, compared to 21% in rural areas
- - - - stagnant surface water, which provides a breeding habitat
      - warm, humid climate throughout the year in low-altitude areas (transmission rates peak after the rainy season, June-November)
    - - population movements between the highlands and lowlands during the harvest period
      - urbanisation; flood excavations and rubbish dumps provide breeding sites
      - irrigation schemes; the construction of canals and the cultivation of rice provide breeding sites
      - misuse of malarial drugs
  - - - there have been measures to eradicate mosquitoes, including periodic spraying of dwellings with insecticides and managing the environment to destroy breeding sites
    - - focus on mass publicity campaigns to minimise potential mosquito breeding sites
      - providing early diagnosis and treatment of malaria (within 24 hours of fever)
      - distributing insecticide-treated bed nets to all households in infected areas
- - - - occurs when the spreading disease moves into new areas, leaving behind its origin or source of the disease. E.g. cholera in Haiti
    - - the spread of an infectious disease through the direct contact of individuals with those infected. E.g. the common cold
    - - a disease has a source and spreads outwards to new areas. Meanwhile carriers in the source area remain infected. An outbreak of TB or Spanish flu is an example of expansion diffusion
    - - a disease spreads through an ordered sequence of places, usually from the largest centres with the highest connectivity to small, more isolated centres. Channelled along road, rail and air transport networks which facilitate contact between carriers and a susceptible population
    - - the probability of contact between carrier and non-carrier is determined by the population density
      - thus people living in proximity to carriers have a greater probability of contracting the disease than those located further away. The distance-decay function is assumed to be geometric in character
      - the number of people infected by an epidemic approximates an S-shaped or logistic curve over time. After a slow beginning, the number infected accelerates rapidly until eventually levelling out, as most of the susceptible population has been infected