Five Most Common Infectious Diseases

Bacteria, viruses, fungi, and parasites are the most common causes of infectious diseases worldwide. Their impact varies from mild to severe and can even be fatal if not treated promptly.

To understand the magnitude of infectious diseases globally, we turn to epidemiology – the study that helps us track disease patterns and their causes across populations.

Some of the most common infectious diseases are:

1. Tuberculosis (TB)
2. COVID-19
3. HIV/AIDS
4. Malaria
5. Influenza (Flu)

Let’s delve into the top facts about each of these diseases.

Image courtesy of GIDEON Informatics: Worldwide Tuberculosis cases

• Tuberculosis (TB) is the world’s deadliest infectious disease. It is caused by bacteria and kills over 10 million people every year (WHO Global TB report 2023).
• TB is caused by a bacterium called Mycobacterium tuberculosis. This bacteria has a unique waxy cell wall that makes it resistant to many antibiotics, and it can survive outside the body for a long time, making it highly contagious. 
• Many individuals have latent TB (LTBI), where the bacteria reside in the body but do not cause infection immediately. The infection may remain dormant until even years later, where if the human host’s immune system weakens, the TB bacteria can cause active infection.
• The most common way to diagnose TB is through the Mantoux TB skin test. Here, a small amount of TB protein is injected under the skin, and the patient is monitored for an immune response.
• TB is preventable and curable. However, although TB is preventable and curable, the rise of multi-drug resistant TB strains (MDR-TB) is a major cause of concern for public health. 

• COVID-19 became the world’s most deadly infectious disease during the COVID-19 pandemic but is now second to tuberculosis. 
• There were 770 million confirmed cases of COVID-19, with almost 7 million deaths reported (WHO COVID-19 dashboard, as of September 13, 2023).
• The development of COVID-19 vaccines is a shining example of how scientific collaboration led to life-saving innovation. Although the SARS-COV-2 virus was new, scientists could sequence its genome quickly and help develop vaccines, diagnostic tests, and treatments against the vaccine.
• mRNA COVID-19 vaccines like those manufactured by Pfizer-BioNTech and Moderna are groundbreaking. The technology introduces a small piece of the virus’s genetic material into the body to stimulate an immune response. 
• The original SARS-COV-2 virus has mutated several times since the pandemic first began in 2019. While not all mutant strains were dangerous, the Delta variant, in particular, caused widespread death and hospitalizations.

Image courtesy of GIDEON Informatics: Worldwide AIDS deaths

• HIV, the Human Immunodeficiency Virus, was first discovered in the early 1980s. It is responsible for causing AIDS (Acquired Immunodeficiency Syndrome). 
• According to UNAIDS, almost 39 million people were living with HIV in 2022, and 1.3 million people were newly infected with HIV the same year. 
• Although the death rate for AIDS has decreased significantly since the eighties and nineties, 630,000 people still die from HIV-related infections each year.
• HIV can be transmitted through unprotected sex, shared needles during drug use, from mothers to their children during childbirth or breastfeeding, and blood transfusions with contaminated blood. 
• AIDS is the advanced stage of HIV infection, where the infected individual experiences severe damage to the immune system. With weakened immunity, people with AIDS are more susceptible to other infections and cancers. 
• HIV and AIDS can be treated through Antiretroviral therapy (ART). The discovery of this treatment was revolutionary, and now, people with HIV can live long, healthier lives. 
• PrEP (Pre-Exposure Prophylaxis) is a preventive medication that can significantly reduce the risk of getting infected with HIV.

• Malaria is transmitted through a parasite and continues to be a global concern.
• Parasites from the plasmodium family cause malaria, with plasmodium falciparum being the most deadly.
• WHO estimates that almost half the world’s population is at risk of getting infected with malaria. 
• According to WHO, in 2021, there were an estimated 247 million cases of malaria globally, with almost 620,000 deaths. 
• The WHO African region has the highest disease burden for malaria, with children under five comprising a staggering 80% of all malaria-related deaths in the region. 
• Malaria is transmitted through female Anopheles mosquitoes that carry the disease-causing parasites to their human vectors when they bite them. 
• Malaria can be prevented by using mosquito nets and repellents, wearing protective clothing, and reducing the amount of stagnant water and open sewage canals.

• Influenza is commonly known as the flu. It is a viral respiratory disease affecting millions worldwide. 
• The flu virus is highly contagious and is transmitted through the air when an infected person sneezes, coughs, laughs, or touches contaminated surfaces. ‘Flu season,’ when flu cases rise, is usually during colder weather, and these outbreaks can cause illness and hospital visits. 
• There are multiple strains of the flu virus—A, B, and C. Influenza A viruses are the most common; however, it’s quite common for one or more variations to infect people each season. 
• The most deadly influenza pandemic was the Spanish flu in 1918, but after the development of effective vaccines, the death rate decreased drastically.
• Preventing the spread of influenza involves improving vaccination rates, practicing hand hygiene, and social distancing when sick.

GIDEON is one of the most well-known and comprehensive global databases for infectious diseases. Data is refreshed daily, and the GIDEON API allows medical professionals and researchers access to a continuous stream of data. Whether your research involves quantifying data, learning about specific microbes, or testing out differential diagnosis tools, GIDEON has you covered with a program that has met standards for excellence.

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