Global infections scenario : Which are the most common ones?

common global infections

Last Updated December 20th, 2021

The story of penicillin: How a rogue mold growth saved humanity

“When I woke up just after dawn on September 28, 1928, I certainly didn’t plan to revolutionize all medicine by discovering the world’s first antibiotic, or bacteria killer. But I guess that was exactly what I did.”

These were the exact words used by Dr. Alexander Fleming to describe the day he discovered that the tenacious and potentially staph bacteria could be destroyed by the use of a mold, a fungus.

When Alexander Fleming returned from a vacation in sunny Scotland to resume his duties as a bacteriologist at the St Mary Hospital in London, he noticed something exceedingly odd happening in one of his Petri dishes.

staphylococcus bacteria

He noticed that the Petri dish where he was growing colonies of the staph bacteria was contaminated with mold. A mold that not only prevented the expansion of the said pathogen but could also be used to counter infections.

This somewhat serendipitous discovery changed the history of mankind forever.

The mold in this story is none other than penicillin notatum – a wonder drug pulled out of the extract of a fungus that proved its worth during the world war.

The surging havoc of infectious diseases

During the 40s the world was anguished with turbulent wars. However, the major killer during these wars was not surprisingly not battle injuries but infections.

Infections – the endless mayhem in our bodies caused by tiny microscopic organism called as microbes that can result in anything between a harmless sneeze to a lethal septic shock.

These have remained one of the biggest killers of humanity since the beginning of civilization.

Be it the disastrous Spanish flu of 1918 that easily wiped out a population as large as 50-100 million or the horrific bubonic plague or “Black Death’ that shrunk the vast demography of Asia and Europe by at least 50%.

Until a few decades ago, infectious and parasitic agents were the number killer of human beings worldwide.

In the year 1997, these collectively claimed about 17 million lives across the globe.

Massive progress made in the development of vaccinations, improvements in sanitation and increased awareness about the high virulence of such diseases have caused a relative decline in the incidence of infections.

However, in case of low and middle countries, the threat of lethal epidemic still looms at large.

As per a 2004 report published by the WHO, 88% of all deaths caused by diarrhea (a gastrointestinal infection brought on by the onslaught of either the rotavirus or the bacteria such as E.coli or Salmonella), was caused by lack of sanitation and contaminated water.

A whopping 99% of these diarrheal deaths occur in low and middle countries.

Toll of diarrhreal diseases

And around 84% of the mortality occurs in children.

Scientists today are frantically in search of cures for these life-threatening epidemics.

Though the danger posed by many infections such as influenza has been mitigated successfully with vaccines, the curse of incurable infections such as AIDS and Ebola still haunts the world.

These minuscule pathogens have been proven to be statistically more dangerous to mankind than atomic bombs or natural calamities throughout history.

But how is it possible that these teeny-tiny microscopic creatures are able to ensue a chain of cataclysmic bodily reactions that could lead to severe damage and even death?

How is that a simple cut or scrape on the skin could poison your blood and lead to septic shock?

And when are we going to find a vaccination for the common cold?

To find an answer to all these questions, we need to go back to the basics of high school biology to understand the exact mechanism of microbe proliferation and learn how a phenomenon known as antibiotic resistance could be next big holocaust.

The events that unfolded in Fleming’s Petri dish

What Fleming had expected to see in his Petri dish was a sprawling colony of the staphylococcus bacteria; the same bacteria that is responsible for sore throats, pus formations, abscess, pneumonia, and even sepsis.

These were one of the most feared infections of those days.

However, a simple blob of mold has inadvertently restricted the growth of this vastly pervasive culture of bacteria.

For the first time it was observed that a fungus, a primitive organism with plant-like features, could counter the toxins given off by a bacterium.

Pathogen Variants

However, bacteria are not the only category of microscopic organism that could be toxic or infectious.

And in many cases bacteria could actually be beneficial for your body (read: gut bacteria).

There is another group of pathogens called as the parasites – something that sucks out nutrition from the host cell for survival- that causes infections in the human body.

However, the most devious category of pathogens is the virus – a microorganism which is one-hundredth the size of a bacteria and responsible for infection in every part of the human body imaginable.

Infections occur when these microbes (yes, fungi included) invade the human body, latch on to specific tissues, hijack the host cell’s nutrients, and multiply rapidly.

The reason why isn’t there any cure for viral infections such as AIDS is because unlike bacteria the virus hides inside the host cell.  Once they invade the host cell, they restructure the elements of the host cell and create further copies of themselves till the host cell burst and meets its end.

Thus, not only are they harder to target because of their small size and obscurity but also their typical metabolism poses a challenge to the immune system.

This is the reason why antibiotics cannot be used to treat viral infections.  And this is also the reason why there is no “cure” for viral infections – be it the cold and flu or the mighty AIDS.

However, the usage of antibiotics to treat viral infections will lead to something called antibiotic resistance.

Why antibiotics cannot destroy virus

It is the phenomenon where bacteria develop resistance or immunity to a particular antibiotic. This could also be a result of overuse of antibiotics (as prescribed medication or consumption of meat treated with antibiotics) or taking an incomplete dosage of antibiotics.

Factors that encourage the massive spread of infections

Lack of sanitation

With around 11-20 million cases reported every year, typhoid is one of the most rampant infections in the planet. It is caused by the bacteria salmonella typhi and is widespread in the tropical and subtropical countries.

The patient develops reddish spots on the face, a high fever, and an array of gastrointestinal issues – from abdominal distension to diarrhea. This disease can also be highly fatal.

In advanced stages it causes enlargement of vital organs such as the liver and even results in internal hemorrhage.  The patient may also get sepsis and encephalitis.

The bacteria spread through contaminated food and lack of sanitation.  Even though vaccines are available for this infection still a large chunk of people residing in poor communities, especially children fall a victim to typhoid and are thus at high risk of mortality.

Lack of sanitation & food contamination

Hepatitis is a viral inflammation of the liver. It is of 5 types – A, B, C , D, E.

Every year almost 1.4 million new cases of Hepatitis A are reported, while there exist more than 300 million people afflicted with hepatitis B. Each year, 1.7 million new cases of hepatitis C are also reported.

This disease can cause irreversible damage to the liver such as fibrosis, cirrhosis, or even cancer.

Hepatitis A and E are spread through contamination of food and water (fecal-oral route), hepatitis C is mainly brought on by unprotected sexual contacts, while hepatitis D transfers by infected bodily fluids.  Hepatitis B and C have the most far-reaching grasp amongst all, comprising of roughly 96% of all cases of hepatitis.

Airborne pollutants and microbes

The common cold is probably the most common viral infection observed across the globe. It is a kind of viral infection, spread mostly by the rhinovirus.

The pathogen affects the upper respiratory tract and thus an individual develops a running and itchy nose with coughs.  Sudden weather changes, high pollution levels, seasonal allergens, and an inherent weak immune system can predispose a person to this infection.

Lack of sanitation & food contamination

Flu is caused by the influenza virus and thus can even persist after strong medications. It affects the lungs and throat along with the nose. Together cold and flu result in 35 billion sick days reported annually across the globe.

According to WHO the death toll by measles is around 367 deaths per day that translates to roughly 134,000 deaths annually.

This viral infection is highly contagious and spreads mostly through infected respiratory droplets suspended in the air.  It is marked by the presence of fever, inflammation in the eyes, and reddish elevated bumps all over the skin.

If left untreated, this infection can have even more dangerous consequences such as diarrhea, pneumonia, bronchitis, corneal scarring, and brain inflammation. It can be prevented by the MMR vaccine.

Marked by highly typical uncontrollable coughs that produce a whooping noise, whooping cough or pertussiss is a severe bacterial infection that mostly affects children.

The coughs are episodic in nature and leave the patient fatigued and in severe chest pain. Children with recurrent pertussis infections require hospitalization and are at high risk of other severe lung infections and even seizures.

Before the vaccine for pertussis was introduced, every year 175,000 cases were reported. It may be fatal in 1% of all children who are diagnosed with the infection.

Did you know that conjunctivitis affects 6 million people every year? Or, that 1% of all primary care hospital visits is due to conjunctivitis? Yes, this particular infection of the conjunctiva ( a thin membrane that covers the eyes and eyelids) is one of the mostly commonly diagnosed infections worldwide.

Air borne diseases

This could be brought on by either pathogens, such as bacteria or virus, or by environmental allergens, such as pollen or dust.

This is a highly communicable disease which can easily spread by sharing of clothes, bedding, and personal care items

Lack of sanitation and even swimming in infected water could result in conjunctivitis. Neonatal conjunctivitis which is spread by the N. gonorrhea bacteria (STD) can even lead to permanent blindness.


Mosquitos and stagnant water

Warm and tropical weather conditions are ideal for microbial and mosquito growth and have thus resulted in the widespread epidemic of malarial infection.

This is a highly communicable disease caused by the Plasmodium parasite which is transferred from the bite of a female Anopheles mosquito.

As per WHO reports, every year roughly 200 million people fall victim to malaria. It is marked by the presence of extremely high fever, chills and shivering, vomiting, and headaches.

In the advanced stage, it can also cause respiratory dysfunctions, low blood pressure, and impaired renal functions. Of all the cases of malaria reported globally, 90% of them are endemic to the sub-Saharan region of Africa.

This disease has a massive impact on the health of children. 66% of all malarial deaths occur among children under the age of 5.

Climate changes


A whopping 2.5 billion people on the planet, roughly 40% of the entire global population resides in areas with high risk of dengue fever.

This infection is caused by the Flavivirus and manifests in the form of fever and excessive joint pain (thus the nickname “break-bone fever”). The vector or carrier of this virus is the Aedes aegypti mosquito that breeds extensively in humid climate and accumulated water.

The main symptoms of this disease are fever, rashes, drowsiness, dehydration, and gastric disorders.  There are currently no vaccines available for this infection.

Every year, around 400 million people are infected with dengue fever and it is the leading cause of deaths among children in many countries.

Unprotected sexual contact

Sexually transmitted diseases are massively widespread across the globe with almost 498 million within the age bracket of 15-49 being affected by it annually.

These diseases can be caused by the virus, bacteria, and even fungi and is spread by either unprotected sexual contacts or from expecting mother to the fetus. AIDS, syphilis, gonorrhea, herpes, and hepatitis B are some of the most prominent STDs.

Unprotected sexual contacts

These are usually characterized by sores or blisters on the skin or the on the genitals, painful intercourse, vaginal bleeding, and warts on skin or genitals.

Women are 10 times more at risk for STDs than men because of their anatomy (shorter urethra allows easy transmission of pathogens inside the body).  Using proper protection during sexual intercourse is the easiest and the most effective preventive method.


AIDS or Acquired Immuno Deficiency Syndrome is perhaps one of the most dreaded infections in the world partly because of its debilitating symptoms and partly because it has no cure.

This sexually transmitted infection has the capacity to completely obliterate one’s immune system that eventually leads to the death of the patient. It is spread by the HIV or the Human Immunodeficiency Virus and spreads mostly by unprotected sexual contact and from expecting mother to fetus.

Contrary to popular myths, this doesn’t spread through touch or sharing of clothes and bedding. It can cause a range of infections such as pneumonia, cheilitis, tonsillitis, mycosis, and diarrhea. It increases the risk of cervical cancer.

Till date, 35 million people have succumbed to AIDS. Every year more than 1.5 million new cases are reported. 70% of all cases are reported in the sub-Saharan region.

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