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Infectious diseases in the 21st century

coronavirus statistics on screen
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Infectious diseases are caused by pathogens and are transmitted from person to person. This article discusses the diseases that have occurred since the beginning of this century, and compares them to the last major disease, that caused by the Sars-cov-2 virus, which causes the disease Covid-19.

Over the past two decades, the world has faced several outbreaks of theses diseases. They have been: Ebola,  Influenza A  (H1N1),  SARS  (severe acute respiratory syndrome),  MERS  (Middle East Respiratory Syndrome), Zika virus    and, most recently,  COVID-19  (coronavirus disease 2019). All of them have a massive global impact in terms of economic upheavals, pressure on local and global public health resources and, above all, human health.

Increase in scientific publications on infectious diseases

When an infectious disease arises, scientific journals and publications are filled with articles talking about the new pathogen. After a disease outbreak, we see a sharp increase in disease-specific publications, demonstrating the ability of the research community to respond quickly to public health needs.

In the cases of the Sars-Cov-1coronavirus, which produced an outbreak in 2002, the number of publications on the https://www.elsevier.com page increased by 1,248%. In the case of  Influenza, it increased by 74%. Ebola 1,311% and Zika 3,319%.

Figura 1. Original https://www.elsevier.com/connect/infographic-global-research-trends-in-infectious-disease

Impact of infectious outbreaks

One way to measure the impact of infectious outbreaks is the number of reported cases as well as the number of people killed. The following infographics show the data of reported cases of each of the diseases as well as the number of deaths from each of them.

The data I show below is reported from the source at the end of the article, in the references. They may not be 100% real since it is sometimes difficult to assess the positive cases and the number of deaths. A clear example is Covid-19,  where it is more than likely that the number of reported cases and deaths are actually quite far from the data given below.

Therefore, these data are taken as a starting point, without any other pretension. Keep in mind that this data is subject to change since for example the covid-19 data will change tomorrow.

Reported cases of infectious diseases

The cases reported as positive for each of these diseases are as follows:

Infectious diseaseCase numbers
Influenza H1N1100.000.000

The infographic of this data would be:

People who died of infectious diseases

Unfortunately, we have to talk about the people who did not survive these outbreaks. The data as of today would be as follows:

Infectious diseaseNumber of deaths
Influenza H1N175.000

An infographic with this data would be:

Infectious diseases


Infectious diseases are caused by pathogens and transmitted from person to person. There are two variables that are usually studied which are the number of reported cases as well as the number of people who died.

In addition, the case fatality rate is usually used which refers to the proportion of deaths among those affected by a disease. In general, this epidemiological measure is calculated as the number of deaths among the number of diagnosed cases multiplied by 100. The case fatality rate for each of these diseases would be as follows:

DeceasedReported casesmortality rate (%)
Sars 774 8.098                        9,56
Influenza H1N1 75.000 100.000.000                         0,08
MERS 842 2.442 34,48
Ebola             11.310 28.616                      39,52
Zika 35                   1.685 2,08
Sars-cov-2 3.882.169        179.261.030                         2,17
TOTAL  3.970.130         279.301.871

In this variable, both mers and ebola cause more deaths in percentage, 34.48% and 39.52% respectively. The Covid-19 caused by the Sars-Cov-2 virus has a percentage of 2.17, although this value is likely to be variable over time since the pandemic is not yet over and as mentioned there are many undiagnosed cases.

Whenever a new infectious disease emerges, the global scientific community works to inform the population and provide mechanisms to combat it such as vaccines (prevents infection) and drugs (treats infection). Without the scientists, our destiny as a species would be compromised because every new epidemic or pandemic threatens our survival.

Tools used

  • R (https://www.r-project.org/)
  • https://piktochart.com/


  • https://www.elsevier.com/connect/infographic-global-research-trends-in-infectious-disease
  • Mers data -> https://wwwnc.cdc.gov/eid/article/25/9/19-0143_article
  • Covid-19 data -> https://www.worldometers.info/coronavirus/
  • Sars data -> https://www.cdc.gov/sars/about/fs-sars.html
  • Zika data -> https://jglobalbiosecurity.com/articles/10.31646/gbio.83/
  • Influenza data -> https://www.cdc.gov/flu/pandemic-resources/burden-of-h1n1.html
  • Ebola data -> https://www.cdc.gov/vhf/ebola/history/2014-2016-outbreak/case-counts.html

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