What is a disease?

This may not seem like a relevant question, but sometimes taking a moment to make sure that we are on the same page is essential, especially when treating complex subjects. 

The simplest definition of a disease would be, a condition that makes the body not work well. An infectious disease is one caused by germs that can spread from person to person, directly or indirectly. Germs, also called microbes, are tiny things everywhere. Most are harmless, but some can make you sick. Germs spread when you touch someone who is sick or through their saliva, blood, or when they cough or sneeze, among others. Germs can also be on things you touch. Insects or animals can carry germs, and so can dirty water, food, soil, or plants.

There are four main types of germs: bacteria, fungi, parasites, and viruses. Bacteria are one-celled microbes that give off toxins and can cause illnesses like strep throat or urinary tract infections. Fungi are simple organisms, including things like mushrooms and yeasts. Athlete's foot is a common fungal infection. Parasites are usually incapable of living on their own at least in one of the different steps in their vital cycle. Protozoa and worms are examples of parasites. Malaria is caused by a protozoan parasite. Lastly, viruses are tiny “capsules” that invade cells, multiply, and make people sick. HIV/AIDS and the common cold are caused by viruses.

Germs cause infections by getting into our body through the skin or inner surfaces like our lungs or stomach. Our body tries to fight them with its defense system, but sometimes the germs win, and we get sick. If our immune system can't stop the germs, we get an infectious disease. Some diseases make germs release harmful things that can damage our body. These diseases can spread to other organs or systems. Sometimes, our immune system fights so hard that it hurts us, called immunopathology.  

Germs vary in how harmful they are, how easily they spread between people, and how long it takes to get sick after being infected. Epidemiologists study how infectious germs are. They use a number called R0 to measure it. For example, COVID-19 had an R0 of 2.5 at first, meaning one infected person could infect 2.5 others. By July 2020, it was as high as 5.7. New variants may spread even faster. In contrast, SARS had an R0 of 3.5, while measles was one of the most contagious diseases with an R0 of 16. This number helps scientists understand how diseases spread.

There are two main types of disease threats to human security: endemic diseases that are always around, and epidemic and pandemic diseases that are sudden and widespread. Endemic diseases are often overlooked, while epidemics and pandemics have been a concern for a long time.

An epidemic is when a disease affects many people in a community or region more than expected, and it can happen at an unusual time. A pandemic is an epidemic that spreads to many countries and continents. Both epidemics and pandemics often involve new diseases or variants with little immunity in the population. They can spread quickly and have a high rate of people getting sick and dying.

Endemic diseases are constant in a specific group of people or area and don't usually spread to other places. For example, malaria is endemic in parts of Asia and Africa. HIV/AIDS is a pandemic, but it has also become endemic in Africa. An outbreak happens when there are more cases than expected or when a new area is affected. If it's not controlled, it can turn into an epidemic. For instance, dengue fever outbreaks have happened in Hawaii, but they were controlled and didn't spread to other parts of the US or the world. An outbreak is considered "out of control" when each sick person infects two others.

Before the 19th century, people's life expectancy was only 29 years, primarily due to diseases and infections during childbirth and wounds. Infectious diseases caused most premature deaths until the late 20th century when non-communicable diseases took over. Improvements in sanitation, vaccines, and antibiotics greatly increased life expectancy, reducing death rates from infectious diseases by 0.8% annually throughout the last century.

While we've made impressive strides in treating bacterial infections, there are limited antiviral drugs for emerging viral infections, and up to this day smallpox seemed like the only disease completely eradicated through vaccination, although now we can see some new cases in war zones. 

The key to controlling infectious diseases is breaking the chain of transmission, which is challenging and requires strong coordination and state capacity. However, there has been substantial progress in reducing mortality rates from infectious diseases. From 2000 to 2010, deaths from HIV/AIDS, TB, and malaria fell by 46%, 36%, and 35%, respectively, in low-income countries, and this trend continued from 2010 to 2020.

Despite declines in deaths from major diseases, the number of disease outbreaks has increased significantly since 1980. Emerging and re-emerging diseases (ERD) are infectious diseases that are on the rise. The WHO focuses on researching the emergence and re-emergence of diseases.

There are at least 30 infectious diseases known to be re-emerging or spreading globally. Tuberculosis, in particular, is making a comeback, with nearly one-third of the world's population having latent TB infections. Additionally, outbreaks of cholera, anthrax, yellow fever, dengue fever, chikungunya, typhoid, West Nile virus, artemisinin-resistant malaria, and plague have occurred.

In 2015, the WHO gathered scientists and health experts to prioritize emerging disease pathogens with epidemic or pandemic potential. They identified seven diseases as top priorities: Crimean-Congo hemorrhagic fever, Filovirus diseases (Ebola and Marburg), highly pathogenic emerging Coronaviruses (MERS and SARS), Lassa fever, Nipah virus, Rift Valley Fever, and an unknown "new disease" requiring urgent attention. Three other diseases, chikungunya, Severe Fever with Thrombocytopenia Syndrome, and Zika, were also considered important. Diseases like tuberculosis, malaria, avian influenza, and dengue were excluded because they already receive substantial funding.

Pathogens can be more deadly than guns, bombs, or even weapons of mass destruction. Among pathogens, viruses stand out because of their potential to cause pandemics, which pose a significant risk to human security. Before the Covid-19 pandemic, experts believed that influenza was the most likely virus to trigger a pandemic.

Influenza viruses are particularly concerning because they constantly mutate, making it challenging to eliminate them through vaccines. In contrast, diseases caused by viruses like measles, mumps, and smallpox have been controlled or eliminated due to their genetic stability, making vaccines effective. Coronaviruses, including those responsible for SARS and Covid-19, share this genetic instability, making them dangerous and potentially resistant to drugs and vaccines.

As Covid-19 continues to produce new, more infectious variants, there is growing concern that vaccines may struggle to keep up.

Predicting pandemic risk involves two factors: the likelihood of a new infectious or re-emerging disease emerging (spark risk) and how easily it can spread through human populations (spread risk). The probability of a severe influenza pandemic, causing around 600,000 deaths worldwide, is about 3% in any given year. For a pandemic with a higher case fatality rate, causing approximately 6 million deaths, the probability is 1%. A pandemic as deadly as the 1918 flu has a probability of less than 0.02%.

Pandemics can overwhelm healthcare systems, leading to more deaths from other diseases due to healthcare shortages. This has a severe impact on developing countries with less prepared healthcare systems.

Endemic diseases, which persist in specific regions, also impose significant costs on many countries worldwide. Most of these countries, mainly in the developing world, lack adequate support to combat diseases that don't easily spread, like neglected tropical diseases. The significance of infectious diseases as a human security issue gained attention during the AIDS crisis in the 1980s, primarily due to concerns about the virus causing instability in African states. While HIV/AIDS has had a devastating impact, there are other endemic diseases with high morbidity and mortality rates that deserve more attention, such as diarrheal diseases.

The Effects of Covid-19

In 2020, a major event occurred when the World Health Organization declared a pandemic called Covid-19. This pandemic affected countries globally, leading to tough decisions by governments. It caused flight cancellations, economic challenges, complete global shut-down and overwhelmed hospitals. The virus didn't care about borders and it impacted people from various backgrounds in the same way.

The media and governments shared many suggestions on dealing with the pandemic's symptoms but often ignored its root causes. These include unrestricted development, changes in food production, encroachment into natural habitats, and ongoing civil conflicts. Instead, much attention focused on developing vaccines, which is impressive but doesn't address the underlying issues like environmental destruction, poverty, and inequality.

In 2020, the world was introduced to Covid-19, a new virus that has raised many questions. Covid-19 is termed a novel virus because it had not been previously seen in humans. It typically shows symptoms like fever, body aches, a persistent cough, and loss of smell. Bats are believed to be its primary reservoir, but pangolins may have played a role as an intermediate host.  

Covid-19 is highly contagious and primarily spreads through airborne aerosols. What complicates matters is that many infected individuals, estimated at 20-40%, show no symptoms. Both asymptomatic and pre-symptomatic individuals can transmit the virus, but the extent of their contagiousness remains uncertain.

The virus has disproportionately affected the elderly and those with underlying health conditions, but it has also caused long-term health issues in young and previously healthy individuals. Some speculate that exposure to a high viral load might contribute to severe cases, but this theory lacks solid confirmation. Additionally, the long-term effects on "long-haulers" are still not fully understood.

Governments failed to prioritize health security despite warnings from organizations like the World Health Organization. Pandemics and epidemics gain political attention during outbreaks but fade afterward. The Covid-19 pandemic highlighted the political and economic consequences of infectious disease outbreaks, but it's uncertain if this will lead to a different approach to health security.

Borders are irrelevant when it comes to health threats, and vaccine nationalism may hinder global health security. While some countries have vaccine advantages, many others lack production capabilities, raising concerns about equitable access and the emergence of new variants.

Climate-related disasters like droughts, wildfires, storms, and floods are increasing, with the Global South bearing the brunt. Take Bangladesh, for instance, one of the world's most climate-vulnerable nations, frequently grappling with storms and flooding. Cyclone Bulbul, a relatively modest Category 3 storm, struck its coast in November 2019. Though it resulted in a relatively low death toll, the loss of over 72,000 metric tons of crops valued at $31 billion exacerbated the country's existing food insecurity. 

Furthermore, climate change in Bangladesh, coupled with the constant threat of storms, leads to a surge in eco-refugees and internally displaced persons (IDPs), intensifying pressure on already overcrowded urban centers. While it may appear that massive storms in Bangladesh have limited global repercussions, the interconnected nature of our world challenges such a narrow viewpoint. 

These disasters have far-reaching consequences, including food insecurity, displacement, and global instability. Addressing climate change is essential to prevent further crises.

Disasters are a big problem, but they often get less attention than they should. They mess up how society normally works and make it hard to cope. Disasters can also push vulnerable groups deeper into poverty, creating traps where it's tough to escape from being poor. On top of poverty, disasters can lead to other problems, like diseases that spread and create complex emergencies. It's strange that even though disasters happen so often, we mostly focus on getting ready to respond after they've already hit instead of preventing them. We should be thinking about long-term solutions like addressing climate change and short-term strategies like reducing disaster risks.

You might think that public health issues don't relate to political science, but the Covid-19 crisis has shown us how interconnected these challenges are with various fields like development studies, disaster studies, environmental studies, humanitarian studies, human rights, public health, and public policy. The global response to this crisis highlights the importance of interdisciplinary approaches to understanding the problems and threats we face as a global community.

The Covid-19 pandemic showed that regardless of a country's wealth and power, diseases can cause significant damage. However, most infectious diseases and disasters have a much more severe impact on developing countries. We need to understand why this is the case by examining the challenges these countries face. 

List of Main Pathogens in Africa, for Humans

Main human diseases

1. Malaria Parasite (Plasmodium spp.):

   - Main Characteristic: Malaria is caused by several species of Plasmodium parasites and is transmitted through the bite of infected Anopheles mosquitoes. It primarily infects red blood cells, leading to symptoms such as fever, chills, and anemia.Malaria continues to be a major cause of death in Africa, with hundreds of thousands to over a million deaths annually, primarily affecting young children.

   - Area of Influence: Malaria is widespread throughout sub-Saharan Africa, with high transmission rates in regions with suitable mosquito breeding habitats.

2. HIV/AIDS (Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome):

   - Main Characteristic: HIV weakens the immune system by attacking CD4 cells, making individuals susceptible to various infections and cancers. AIDS is the advanced stage of HIV infection. HIV/AIDS has claimed millions of lives in Africa since the epidemic began. In recent years, the annual death toll has decreased due to improved access to antiretroviral therapy, but it still remains a significant health challenge.

   - Area of Influence: Sub-Saharan Africa has the highest prevalence of HIV/AIDS globally, with Southern and Eastern Africa being the most affected regions.

3. Tuberculosis (Mycobacterium tuberculosis):

   - Main Characteristic: Tuberculosis primarily affects the lungs and can lead to symptoms such as persistent cough, weight loss, and fatigue. It is transmitted through the air when an infected person coughs or sneezes. Tuberculosis is a leading cause of death in Africa, with hundreds of thousands of deaths annually.

   - Area of Influence: Tuberculosis is widespread in Africa, with high burdens in countries like South Africa, Nigeria, and Kenya.

4. Ebola Virus:

   - Main Characteristic: Ebola causes a severe and often fatal hemorrhagic fever, with symptoms including fever, vomiting, diarrhea, and internal bleeding. It is transmitted through contact with infected bodily fluids. Ebola outbreaks have resulted in thousands of deaths during major outbreaks, but the number of annual deaths varies widely depending on outbreak occurrence.

   - Area of Influence: Ebola outbreaks have occurred in several Central and West African countries, including the Democratic Republic of Congo, Guinea, Sierra Leone, and Liberia.

5. Yellow Fever Virus:

   - Main Characteristic: Yellow fever can cause fever, jaundice, and bleeding. It is transmitted by Aedes mosquitoes. Yellow fever outbreaks can lead to a significant number of deaths in affected regions during outbreaks, but annual deaths may be lower in non-outbreak years.

   - Area of Influence: Yellow fever outbreaks can occur in parts of West and Central Africa.

6. Cholera (Vibrio cholerae):

   - Main Characteristic: Cholera causes severe diarrhea and dehydration. It is primarily transmitted through contaminated water and food. Cholera outbreaks can lead to thousands of deaths in affected areas during outbreaks, but the annual death toll can vary.

   - Area of Influence: Cholera outbreaks are common in areas with poor sanitation and access to clean water, including parts of Africa.

7. Lassa Fever Virus:

   - Main Characteristic: Lassa fever is an acute viral hemorrhagic fever. It is transmitted through contact with infected rodents or their excreta.Lassa fever can lead to deaths, but the annual number of deaths may not be as high as some other diseases on this list.

   - Area of Influence: Lassa fever is mainly found in West African countries, including Nigeria, Sierra Leone, and Guinea.

8. Trypanosoma brucei (African Trypanosomiasis or Sleeping Sickness):

   - Main Characteristic: Trypanosomiasis causes fever, neurological symptoms, and sleep disturbances. It is transmitted by tsetse flies.

   - Area of Influence: Sleeping sickness is endemic in some parts of sub-Saharan Africa, particularly in regions where tsetse flies are prevalent.

9. Schistosomiasis (Schistosoma spp.):

   - Main Characteristic: Schistosomiasis is a parasitic disease that affects the urinary and intestinal systems. It is acquired through contact with freshwater contaminated by infected snails. Sleeping sickness leads to deaths, but the numbers may not be as high as some other diseases.

   - Area of Influence: Schistosomiasis is prevalent in many freshwater areas across sub-Saharan Africa.

10. River Blindness (Onchocerca volvulus):

   - Main Characteristic: River blindness is caused by a parasitic worm transmitted through the bite of infected black flies. It can lead to skin lesions and vision impairment, including blindness. River blindness can cause significant morbidity and vision impairment but may not always result in deaths.

   - Area of Influence: River blindness is endemic in parts of West and Central Africa.

11. Buruli Ulcer (Mycobacterium ulcerans):

   - Main Characteristic: Buruli ulcer is a skin disease that causes open sores and ulcers. It is believed to be transmitted through contact with contaminated water or soil. Buruli ulcer is not typically fatal, but it can lead to disability and long-term health effects.

   - Area of Influence: Buruli ulcer has been reported in several West and Central African countries.

12. Rift Valley Fever Virus:

   - Main Characteristic: Rift Valley fever can cause fever, severe illness in animals, and in humans, symptoms ranging from mild flu-like illness to severe hemorrhagic fever. It is transmitted through the bite of infected mosquitoes.  Rift Valley fever can lead to deaths during outbreaks, but annual numbers may vary.

   - Area of Influence: Rift Valley fever outbreaks have occurred in parts of East and North Africa.

13. Dengue Virus:

   - Main Characteristic: Dengue fever causes flu-like symptoms, including high fever and severe joint pain. It is transmitted by Aedes mosquitoes. Dengue can lead to deaths, but the number of annual deaths in Africa may not be as high as in some other regions.

   - Area of Influence: Dengue outbreaks can occur in parts of Africa, particularly in urban areas with Aedes mosquito populations.

References

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