This section provides a summary of the possible human disease outbreaks which may have a disaster risk.   

For specialised opinion on any human disease or other health issues, please refer to your doctor or clinic or to the City Heath Website.

The City of Cape Town’s Health Directorate continuously monitors all aspects of the population’s health. For example, the Infectious Disease Control Unit investigates environmental factors relating to the spread of notifiable infectious diseases, and putting preventative measures in place to limit the spread thereof. They compile case histories with regard to Hepatitis, Typhoid and Cholera, etc. and do Cholera risk monitoring by means of placing "Moore Pads" at selected sampling points, and analising results.

These are examples of some of the diseases which are prevalent in the City of Cape Town:

Tuberculosis (TB)  
Tuberculosis, including pulmonary TB and lung disease, is a common and serious condition occurring in Cape Town. The early symptoms are a cough for more than two weeks which produces phlegm, coughing up of blood, nightsweats, loss of weight and shortness of breath. These symptoms do not mean you have TB but it would be advisable to have yourself screened for TB if you have them.

Municipal clinics provide a service where people are screened for TB, given treatment if they have TB and their contacts are screened should this be necessary. Arrangements can be made for those suffering from TB to receive treatment at work or in the community. Preventative treatment is given to children who have been exposed to TB. Social assessments are done and access to social support is provided where TB patients qualify for it.

TB treatment takes from 6 to 8 months but it is important for all TB clients to complete their full course of treatment. For clinics which provide a TB service, click here.

HIV/Aids    
The City's clinics offer the following services to minimise the spread of HIV/Aids and treat infected people:

• Free condoms
  
• Counselling and testing for HIV/Aids
  
• Treatment of associated (opportunistic) infections and monitoring of clients suffering from HIV/Aids infection (non hospital care)
  
• Prevention of Mother to Child Transmission (PMTCT)
  
• Some clinics supply and treat clients with Antiretroviral (ARV) Treatment

Other prevalent diseases 
Other prevalent diseases include:

• Diarrhoeal and Gastro-Enteritis
  
• Ischaemic heart disease and heart failure
  
• Diabetes Millitus
  
• Hypertensive disease and stroke
  
• Pneumonia
  
• Cerebrovascular diseases
  

Background to Communicable Diseases
Human disease may be an important primary cause of disaster events, but may also be a very important secondary risk in the aftermath of disasters triggered by other causes - such as floods, earthquakes, fires and the like.

Chain of infection
Communicable diseases occur as a result of an interaction of disease-causing agent (pathogen), transmission process and host (usually humans and/or animals). There is a vast array of possible pathogens. Apart from reliable identification of the specific organism involved in a disaster episode, the following aspects are of crucial importance in judging the risk of specific pathogens to cause an outbreak of disastrous proportions:

• Infective dose (number of organisms required to cause infection)
  
• Pathogeni (ability of the pathogen to produce disease, measured by the percentage of persons exposed to the pathogen who will develop the disease)
  
• Infectivity (the ability of the pathogen to invade the host such as a human or animal)
  
• Virulence (an indication of the severity of the disease)
  
• Incubation period (time between entry of the pathogen into the host and the appearance of the first sign or symptom of the disease. This can vary from a few hours to weeks or even years)
  
• Condition of the host (persons who are not in good health because they are already burdened by malnutrition, other diseases, poor housing and sanitation, etc. are more susceptible to infection)

Information on these important attributes is essential to predict the scale of the outbreak and to decide how to manage the consequences most effectively.

Low probability - high consequence events
Certain health-related events may be rare or only occur after a series of unrelated factors all happening at the same time. This will include the introduction of a life-threatening disease hitherto unknown in the area or an outbreak of a disease that causes severe quarantine measures to be introduced. Even though the chance may not be great, when such an event happens, the ripple effects can seriously jeopardize survival, food production and movement of people or the economic stability of the area. These hazards are referred to as "low probability - high consequence" events. Such events require particular co-operation between the public and private organizations to cope with the domino effects of the consequences.     Usually individuals and organizations do not take preventative action unless there are incentives to do so and thus the co-ordination to deal with such events is of crucial importance.

Food safety and food insecurity
High seasonal and year-to year variability in food supplies - often the result of unreliable rainfall and insufficient water for crop and livestock production - are major contributors to chronic under-nutrition and food insecurity. Drought affects health through several pathways. In the most extreme case being famine the number of deaths associated with insufficient food consumption, increases substantially. Famine often occurs when a pre-existing situation of malnutrition worsens.
 
Conversely, the damage wrought by severe floods extends beyond the loss of the present season's crops. The damage to soil, agriculture and infrastructure can cause food insecurity for many years to come. Poor people, and especially those living in marginal environments, are most vulnerable to food insecurity during times of disaster. The following groups may be most at risk for under-nutrition due to food insecurity or diseases carried by contaminated food:

• Rural smallholder producers
  
• Pastoralists (emerging farmers, small-scale farmers etc.)
  
• Rural wage labourers
  
• Urban poor people
  
• Refugees and displaced people
  

Even during everyday (non-emergency) situations, the importance of food safety is often not fully appreciated despite a constant increase in foodborne illnesses worldwide.    Numerous outbreaks of salmonellosis, cholera, enterohaemorragic Escherichia coli infections and hepatitis A have occurred in recent years in both industrialised and developing countries. In addition, many of the re-emerging or newly recognized pathogens are foodborne or have the potential of being transmitted by food and/or drinking water. The emergence of more foodborne pathogens can be expected because of changing production methods, processes, practices and habits.   

During the early 21st century, foodborne diseases can be expected to increase, especially in developing countries, in part because of environmental and demographic changes. These vary from climatic changes, changes in microbial and other ecological systems, to decreasing freshwater supplies.  

However, an even greater challenge to food safety will come from changes resulting directly in degradation of sanitation and the immediate human environment. These include unplanned urbanization and migration and mass production of food due to population growth and changed food habits. Mass tourism and the huge international trade in food and feedstuffs are causing foodborne and feedborne pathogens to spread transnationally. As new toxins are identified and new toxic effects are recognized, the health and trade consequences of toxins in food will also have global implications.   

Meeting the huge challenge of food safety in the 21st century will require the application of new methods to identify, monitor and assess foodborne hazards. Both traditional and new technologies for assuring food safety should be improved and fully exploited. This needs to be done through legislative measures where suitable, but with much greater reliance on proper testing and inspection.

Water-related diseases
By far the majority of water-related pathogens are associated with contamination of water sources by poorly treated or untreated excreta. Many classes of pathogens excreted in faeces are able to initiate waterborne infections. These are bacterial pathogens, including enteric and aquatic bacteria, enteric viruses, and enteric protozoa. Especially protozoa are strongly resistant to die-off in the water environment and also resistant to most disinfectants.

Diseases which are  primarily sexually transmitted
The most important disease in this group and one that has taken a heavy toll in the Cape already is HIV/Aids.

The human immunodeficiency virus (HIV) renders the infected person's immune system fatally damaged over time. Such individuals cannot mount a defence against any pathogens (bacteria, viruses, etc) that enter their systems and they eventually succumb to overwhelming disease. During the phase that their immune systems are severely damaged or when the sufferers develop full-blown auto immunodeficiency syndrome (AIDS). Aids sufferers are particularly prone to respiratory illnesses (TB, pneumonia, etc) and diarrhoea from various organisms. Thus the disease process makes the sufferers much more vulnerable to environmental pollution and infections. Some City clinics supply and treat clients with Antiretroviral (ARV) Treatment. ARV’s are also available at Provincial facilities.      A large proportion of HIV-positive people in a population affected by disaster may mean that the death toll and the morbidity from primary emergencies as well as the secondary fall-out of such emergencies can be much higher than in a healthy population.

Poliomyelitis
Poliomyelitis is a highly contagious viral infection that affects the nervous system. People can be infected with polio when they eat food or drink water contaminated with the virus or when they come into contact with an infected person's faecal matter or saliva. High numbers of viruses are excreted in faeces. In areas with even a few polio cases, all sanitation failures or situations where untreated sewage contaminates water sources will increase the risk of spread of polio. This also implicates rivers that picked up untreated sewage while flowing past human dwellings where the water is used for drinking or irrigating food crops. Contact with open ground where faecal matter has been deposited or overflowing drains also represent a significant risk. Houseflies are also implicated in the spread of the virus when landing on food or other surfaces after having been exposed to infected faecal matter. Thus all informal settlements in Cape Town are especially at risk and much of the food produced using contaminated irrigation water also represents significant risk should the polio virus enter the country. The transmission risk is however not confined to poorer areas - but it is higher under those circumstances. South Africa's last confirmed case of polio was in 1989.

Viral Hemorrhagic Fevers
A case of Marburg fever was identified in the 1970s in a tourist visiting several African countries to the north of South Africa; nosocomial transmission to two persons was identified at that time. One case of nosocomial transmission of Ebola has been reported (the patient with the index case was flown down to South Africa from Gabon); however, no endemic transmission of Ebola virus occurs in South Africa. That the nosocomial transmission of Ebola virus was limited to a single person despite the fact that the diagnosis of the index case was not made until a number of weeks after the patient entered the country is a tribute to the standard of medical care in South Africa. Congo Crimean Hemorrhagic Fever is endemic in southern Africa, but as the vector tick rarely bites humans, not many human cases have been found. Epidemics have been associated with infections in rural communities particularly of farmers and workers who slaughtered infected cattle. An epidemic among ostriches occurred in 1997.

Typical diseases that may affect displaced populations during times of disaster in Cape Town:

Vector-associated disease
Few vector-borne diseases are noted as primary causes of disasters across the world, but many instances of secondary aggravation of existing emergency situations by the added complication of vector-borne risks exist. Some disasters can give rise to increases in the populations of vector or nuisance species, usually insects or rodents. Floods may create new mosquito breeding sites in disaster rubble and stagnant pools. A general breakdown of sanitation may favour the multiplication of houseflies and rodents. People living in partially destroyed houses or primitive shelters may have lost the normal protection afforded by screened windows or mosquito nets. Serious infection hazards may arise when massive migrations bring people of different origins together in temporary camps infested with disease vectors. Under such conditions, people who are relatively immune carriers of parasites can set off disease transmission cycles to which weaker people and people who are not immune fall victim.  Fly control is likely to have a positive impact on health in most post-disaster situations, particularly when sanitary conditions are poor and diarrhoea, Shigella dysentery, or typhoid prevalence are high. When wild or domestic host animals have been killed or driven away by disaster, ectoparasites, such as ticks, bugs, lice and fleas, may invade a community and produce a serious additional risk of zoonotic vector-borne disease. Another, related, vector-borne disease risk may arise when refugees enter territory formerly occupied only by wildlife and accompanying parasites. Examples of diseases that may then emerge include a plague (from rats) and viral haemorragic fever from ticks.

Vectors and diseases that are likely to be present in emergency settlements are of particular importance:

Vector:                   Main diseases:
Mosquitoes             Malaria, yellow fever, viral encephalitis, filariasis
Houseflies             Diarrhoea, dysentery, conjunctivitis, typhoid fever, trachoma
Cockroaches           Diarrhoea, dysentery, salmonellosis, cholera
Lice                       Endemic typhus, pediculosis, relapsing fever, trench fever,
 skin irritation
Bedbugs                Severe skin inflammation
Ticks                      Rickettsial fever, relapsing fever, viral encephalitis, borreliosis
Rodent (fleas)       Bubonic plague, endemic typhus
Rodents  Rat bite fever, leptospirosis, salmonellosis, melioidosis

Influenza
Influenza is a highly contagious, acute febrile respiratory illness that results in global morbidity and mortality annually. Influenza is both an emerging and re-emerging disease.    Health authorities agree that the world is overdue for a pandemic of influenza. A pandemic can happen when different influenza virus strains mutate into a new strain that people's bodies have no immunity against and that is easily spread from person to person. Three pandemics occurred in the 20th century. It is impossible to predict when the next pandemic will occur and what the severity of the illness will be. Signs of a build-up in the risk have already been seen in the development of Severe Acute Respiratory Syndrome (SARS) and the outbreaks of avian flu originating from the Far East. Avian influenza (H5N1) has the potential to cause a pandemic  – refer to the Animal Disease Outbreak section for more background information on this disease.

Communicable diseases already manifest in Cape Town
HIV/Aids and TB together were consistently the leading cause of death in Cape Town over the past five years. The emergence of resistant strains of TB greatly increased the risk of primary or secondary outbreaks of this difficult to treat condition. Multidrug-resistant or MDR-TB is resistant to the firstline anti-TB drugs. If the infection is also resistant to several other drugs used to treat the disease, the condition is referred to as extreme drug-resistant (XDR) TB. Effective MDR-TB management requires improvements in general TB control but also specific responses designed to curb MDR-TB. The Western Cape has the best TB outcomes in South Africa, thanks to enormous investments in TB control, but despite this MDR- and XDR-TB cases are increasingly being reported.

Some important diseases and an estimation of their disaster risk potential: 
 
By drafting your own Family Emergency Plan and identifying all your risks, including those hazards affecting your own environment, you can make a positive contribution to preparedness.