Posted in Science & Nature

Exponential Growth

Imagine that you have won a strange lottery where they give you two options of payment: they can either pay you one million dollars up front, or they can pay you one cent on the first day, then double the amount you have every day for a month (i.e. 1 cent on day 1, 2 cents on day 2 etc.). Which would you choose?

It may seem obvious that the $1 million up front is far better than accumulating a few cents every day. But by the end of the month (day 31), you would actually have accumulated $5.37 million. How did this happen?

The secret to this extraordinary increase is the power of exponential growth. If you double a number constantly at a regular interval, it grows at a staggering rate. Let us look at the above example again.

On day 1, you have 1 cent. By day 10, you already have 2(10-1) = $5.12. Now we can see that instead of mere cents, we are gaining $5 in one day.
By day 15, you have $163.84. Now the doubling nets you another $163.
By day 20, you suddenly have $10,485.76.
We pass $1 million at day 28 where we have $1.34 million.
Day 29 you have $2.68 million and you can see how we end up with $5.37 million – over five times the amount we would have received compared to the first option.

This shows the sheer power of doubling. It is an important principle to grasp as we see exponential growth all around us in life. Nuclear chain reactions undergo exponential growth to power nuclear reactors. Positive feedback in speakers undergoes doubling amplification, resulting in the sharp screeching sounds. Compound interest follows exponential growth, allowing investments to give substantial returns over time (or result in crushing debt). Bacteria divide in two each time, resulting in a rapid population boom.

Understanding exponential growth also helps us make sense of scary situations such as pandemics. Viral infections are spread from one person to multiple people, represented by a basic reproduction number (R0). In the case of the COVID-19 (2019 coronavirus) pandemic, the R0 was between 2 and 3, meaning that left unchecked, the number of infected individuals would essentially double every few days.

Although this seems obvious, if you didn’t know about exponential growth, it would be terrifying to hear that one day you have 8 cases in a country, but in a fortnight, there are over 1000 cases, with each day presenting increasing numbers of newly infected patients. The media preys on this effect by providing anxiety-inducing headlines. But in reality, the headlines might as well read: “virus continues spreading in predictable exponential fashion“.

Another strength of knowing about exponential growth in a pandemic is that it lets us predict what would happen without any intervention. The number of cases would explode in a matter of weeks, resulting in catastrophic numbers of unwell people taken off the workforce, accompanied by mass casualties. Hospitals would be completely overrun, crippling the nation’s healthcare system and resulting in even more deaths as the infection runs rampant.

Therefore, efforts to reduce the spread of the virus through social distancing and effective quarantining are vital to reduce the rate of exponential growth, flattening the curve and making the number of cases more manageable for the healthcare system to deal with.

Posted in Psychology & Medicine

Typhoid Mary

New York City, 1901 – an upper-class family presented with fevers and diarrhoea, diagnosed with the infection typhoid fever. This was unusual as typhoid fever was classically associated with poor hygiene, overcrowding and lower socioeconomic status households. It was atypical to see typhoid fever in upper-class households. Within a year, a lawyer and his household fell ill to the same disease – 7 out of 8 people contracted typhoid. Another case emerged 5 years later in Long Island, New York – an area where typhoid fever was very uncommon. This time, 10 out of 11 family members were hospitalised with typhoid. Countless families fell victim to typhoid fever within this year and people started becoming curious as to the cause of this epidemic.

In 1906, typhoid researcher George Soper began investigating the epidemic and found a common link between all of the families who became sick. They had all at some point employed a cook by the name of Mary Mallon. Soper noticed that Mallon had worked for each of these families roughly three weeks before each of them fell victim to the illness, upon which she would leave the job for another family. Soper approached Mallon to obtain urine and stool samples to prove this, but Mallon adamantly refused and denied any responsibility in her possible role in spreading typhoid as she “was not sick”.

Eventually, the New York City Health Department appointed Dr Sara Josephine Baker to handle the situation. Mallon still refused to comply with the investigation and had to be taken into custody by the police. She was forced to be tested while in prison, which proved that she was an asymptomatic carrier of typhoid fever. Doctors discovered that she had a significant growth of typhoid bacteria in her gallbladder. It was determined that Mallon has infected the families through preparing and serving food (she was famous for her ice cream) with poor hand hygiene.

Due to her non-compliance to the order of restricting her from being a cook, Mallon was quarantined for the rest of her life until she died from a stroke in 1938. Mallon – or as the media called her, “Typhoid Mary” – was the source of at least 51 confirmed typhoid fever cases, three of which were fatal. Some estimates say she could have been responsible for as many as 50 deaths as she had worked under many aliases. All because she did not wash her hands properly.

Posted in Psychology & Medicine


In 1976, an outbreak of a viral illness was identified in Sudan. Patients would present with symptoms of high fever, headache, vomiting, diarrhoea and a spotted rash, but would rapidly deteriorate in health. Within days, patients showed signs of decreased blood clotting, such as bleeding from intravenous line sites, having blood in their vomit and stool, or bleeding from essentially any bodily orifice. If untreated, patients would die within two weeks of shock (very low blood pressure), kidney failure or bleeding into the brain. The outbreak killed 151 people before it disappeared.

Later in the year, a headmaster at a school in Zaire developed a similar disease after travelling to the Ebola River. He died two weeks later. Soon after, people he came in contact with after his trip died of similar symptoms. The World Health Organisation investigated this epidemic and realised that the disease was caused by a new type of virus, which was named ebola virus. Due to its symptoms, the disease caused by the virus is named ebola haemorrhagic fever.

Since the discovery of the disease, occasional ebola outbreaks were seen in various parts of Africa, mainly around Congo and Uganda. Each time, the disease would rapidly claim the lives of hundreds of people and then vanish. This is because ebola virus was so effective in killing people (with a death rate of 90% in one outbreak), that it would kill the infected person before they spread the disease further.

The virus can be spread through any bodily fluid, including blood, tears, semen and sweat. Because of this, once an infected patient is brought into hospital, the disease can spread rapidly throughout the building and infect many patients and hospital staff if proper precautions are not taken. Fortunately, the virus is not known to spread when the patient is in the incubation period (when they are infected but have not shown symptoms yet).

The origin of the virus has been traced back to fruit bats (like many other serious viruses). Fruit bats have extremely powerful immune systems to protect their cells from the harmful metabolites produced by flying, allowing bats to harbour deadly viruses without succumbing to them. These viruses have also evolved to withstand the high temperatures produced by flying (which involves significant muscle work), meaning they can easily survive the high fevers they cause in humans. The transmission from bats to human in modern times is likely attributed to deforestation and humans encroaching into the bats’ native territory.

The current epidemic that originated from West Africa is the biggest ebola outbreak so far, having infected over 9000 people and claiming the lives of over 4500 people (October 14, 2014). However, this is likely a grossly underestimated number. The epidemic is focussed mainly in Guinea, Sierra Leone, Liberia and surrounding countries, but has infected foreign workers and volunteers who have been repatriated to be treated in their home country.

Despite a robust effort from the WHO to try and curb this epidemic, the infection rate continues to climb due to various factors, such as traditional funeral rites involving touching the deceased person’s body, which is still infective after death. There are currently no effective vaccines or treatments and the only thing that can be done is supportive treatment in an intensive care unit where the patient can be adequately hydrated and monitored. Like with most communicable diseases, the most effective treatment is preventing the disease from spreading through education, rigorous infection control protocols and improved healthcare systems in the affected countries.

Posted in Science & Nature


What is the best or easiest way to protect yourself from an alligator attack? Obvious answers aside (such as avoiding them), it is to use something like an elastic band or a rope to tie their snout shut. Alligators have the strongest bite in the natural world – clocking in at about 2125 pounds of force (about 966kg). The sheer force of the bite is enough to crush the victim and kill them instantly. Even if the victim survives, there is a serious risk of being left with a permanent disability or die from an infected wound.

Although the force of the bite is incredible thanks to its extremely strong jaw muscles, alligators do not have nearly enough the same strength when opening their jaws. This means that a simple elastic band is enough to keep their jaws shut, leaving the alligator helpless and giving you a chance to run before its friends come to find you.

Image result for alligator jaw closed shut

Posted in History & Literature


In many cultures (especially in Asian countries), the public conception of doctors has changed where surgeons are considered the “real doctors”. This is particularly evident in Asian dramas where main characters tend to be surgeons, saving the patient’s life with dramatic operations and charisma. The idea that surgeons are superior to physicians may go as far as some adults advising medical students to become surgeons for a higher status (again, more evident in Asia). However, as the root of surgery is completely different from that of medicine, technically it is a misnomer to call a surgeon a “doctor”.

This is reflected in the relatively unknown fact that a fully-trained surgeon is referred to as “mister”, not “doctor”. To understand why surgeons call themselves Mr., we must look into the origin of the surgical discipline.

In ancient times, surgery was limited to treating flesh wounds and setting bones (with some exceptions such as trepanation), such as those sustained during battles. Other than the odd few cases of specialised surgeons such as Galen of ancient Greece and Hua Tuo of ancient China, it is hard to find records of doctors employing surgery as a form of treatment. This was mainly due to two reasons: that surgery was considered a “dirty, unrefined” form of treatment, and that surgery was too risky.

For a long time, especially in the Western world, surgery was considered to be of a lower status compared to medicine. It was considered more of a craft tradition – something which physicians believed was beneath them. Because of this, surgeries were mainly performed by barbers in medieval Europe. One can still find evidence of a barber’s alternative historical role on the barber’s pole, which has white, red and blue stripes. The white stripe symbolises bandages, the red symbolises arterial blood and the blue symbolises venous blood. This originates from the practice of bloodletting, where white bandages wrapped around a pole would get dyed red from the blood, giving the appearance of the barber’s pole. The profession of “surgeon” did not formally appear until around the 18th century when a Guild of Surgeons was formed in England. However, physicians refused to accept surgeons as equals for a further century. When they did come to accept that surgery was a legitimate form of medical treatment, the surgeons decided that they did not want to be assimilated as doctors, so they chose to keep their title of “mister” to distinguish themselves from physicians.

The reason why surgery was considered an unrefined art in the past mainly focuses on three issues: bleeding, pain and infections. Before modern surgical developments, uncontrolled bleeding was a real issue in surgery. This not only made surgeries extremely messy, but it was also dangerous for the patient as patients would often die from shock (dangerously low blood pressure). On top of this, anaesthetics was only introduced in the late 19th century, meaning before that, patients had to suffer the pain of their flesh being cut and stitched with no relief. Of course, this meant that surgeries were almost always a brutal scene, with the agonising screams of the patients filling the room, while they sprayed blood everywhere. Lastly, even if the patient somehow survived the surgery without bleeding out or dying from the stress and pain, there still remained a high risk of post-operative infection. Thus, surgeries were most often unsuccessful and were considered a barbaric form of treatment with no promise.

Thanks to medical advancements, surgery has become an important aspect of medicine, where one cannot live without the other. However, the tension still remains between physicians and surgeons, with each profession jokingly mocking the other whenever a chance arises.

Posted in Psychology & Medicine

Sleeping Sickness

A woman travelling in Africa is bitten by what appears to be a mosquito. She swats the insect and keeps on going about her journey. The next week, she finds that she has a small nodule where she was bit. She is also feeling slightly unwell, with fever and fatigue. Over the following two weeks, her fever worsens (coming and going intermittently) and she notices large lumps along the back of her neck. By this stage, she is experiencing muscle and joint pain as well. After returning home from her trip, she finds that her symptoms have not resolved. On top of her fever and pains, she begins experiencing headaches, mood swings, lethargy, confusion, clumsiness, delayed response to pain, sleepiness during the day and insomnia at night. She begins to worry that something is wrong, but she believes that it is a bad flu and does not see a doctor. Her symptoms worsen with time (sleeping up to 15 hours a day), until one day, she falls asleep and does not wake up. She is taken to a hospital, where it is discovered she is in a coma. She dies within a week.

This is the typical presentation of sleeping sickness, also known as human African trypanosomiasis. It is an infectious disease caused by a protozoan parasite called Trypanosoma brucei (comes in two types: T. brucei rhodesiense (East African type) and T. brucei gambiense (West African type)), which is transmitted by tsetse flies – a bloodsucking fly endemic to sub-Saharan Africa (there are also case reports of sexual transmission between people). When infected, the parasite rapidly proliferates in the patient’s bloodstream. It is not detected by the host immune system, thanks to a surface protein called VSG. This allows it to spread through the patient swiftly and silently via the circulatory and lymphatic systems. The early symptoms (intermittent fever, rash, lymph node enlargement), typically presenting about a week or two after infection, are due to the parasite spreading through the blood and lymph. As the infection spreads, the parasites begin to invade the central nervous system (although in the West African type of the disease, patients often die from the toxic effects of the parasite replicating in the blood before they reach this stage).

As the infection spreads through the CNS, it causes the neurological symptoms described in the case. The sleepiness (from where the disease gets its name from) worsens as the disease progresses, with patients finding it difficult to wake up in the morning, even sleeping for over 20 hours. The sleepiness is caused by a chemical called tryptophol, which is produced by the parasite. Essentially, the neurological symptoms appear as if the person’s brain is slowing down, until they fall into a coma, resulting in death without treatment (usually within 2~3 years since the infection).

Sleeping sickness is invariably fatal unless treated early. Once the patient reaches the second stage (neurological phase), treatment becomes very difficult. The current first line treatment is a drug called melarsoprol, which is a form of arsenic. Because of its toxic nature, it is extremely dangerous and there is around an 8% chance of the patient dying from side effects. Fortunately, there are less dangerous and more effective treatments such as eflornithine (which only works for the West African type) being developed.

Posted in Psychology & Medicine

Laughter Epidemic

It is said that laughter is infectious. In 1962, an extreme case of “laughter infection” happened in village in Tanzania. The phenomenon originated in a boarding school for girls. On January 30, three girls spontaneously burst out in laughter and could not stop themselves from laughing. Soon after, the whole class was suffering from fits of uncontrollable laughter. The “infection” then spread throughout the school, claiming 95 of the 159 students over a stretch of two months. This strange symptom of uncontrollable laughter lasted anywhere from a few hours to 16 days. Interestingly, teachers were not affected and only girls between the ages of 12 to 18 were affected. By March 18, the school was forced to close down due to students not being able to focus during class.

The laughter epidemic was not localised to the school. After the school shut down and the girls returned home, fellow villagers were afflicted by the laughing disease, resulting in 217 villagers being “infected” by May (mostly children and teenagers). By June, the laughing epidemic spread to another nearby school, affecting 48 girls. The epidemic then went on to claim two more schools, forcing them to close down. By the time the epidemic died down (6 to 18 months after “patient zero”), it had affected over a 1000 people and shut down 14 schools.

So what was this strange disease? Was it some new viral infection causing neurological symptoms? Was it a toxin in the water supply? The answer was even simpler: mass psychogenic illness, also known as mass hysteria. Mass hysteria is a psychological phenomenon that occurs in groups placed in high-tension situations, such as within an airplane. This setting is perfect for triggering a mass delusion, causing the person to believe they are suffering from a physical disease. The trigger is usually another “patient” and the hysteria spreads like wildfire, usually by people seeing affected victims. Although the above case makes mass hysteria look like a harmless, amusing phenomenon, psychosomatism (when the mind tricks the body into thinking it is sick) can cause symptoms such rashes, fevers, vomiting and even paralysis. In fact, all of these symptoms were also reported during the Tanganyika laughter epidemic.

Posted in Psychology & Medicine


Scrubs is the uniform that surgeons, anaesthetists, emergency department doctors and nurses wear for the freedom and mobility required in activities such as surgery and CPR. Also, since it is owned and washed by the hospital instead of being privately owned, it is more hygienic and helps prevents infections. A noticeable trait of scrubs (and also surgical gowns) is that almost every hospital uses a shade of blue or green instead of white. Why is this?

The reason being, looking at a surgical scene for a long period of time can cause eye fatigue and afterimages due to the redness of blood and organs. Afterimage is a phenomenon that occurs when the retina becomes insensitive to a strong colour and instead making the complementary colour stand out more. Ergo, a surgeon looking at blood and organs for too long will see afterimages of a blue shade, which may cause accidents to happen as it overlaps on white surfaces or the surgical field. Clothing of blue or green colour neutralises the afterimage and is much easier on the eyes, reducing the fatigue. Lastly, blue-green colours have a calming psychological effect, which helps in a high-tension, stressful environment such as in an operating theatre.

Posted in Psychology & Medicine


Among the thousands of signs and symptoms in the field of medicine, there is one that every doctor and medical student knows since the development of medicine. Clubbing is an easily noticeable sign in a patient’s fingers that can have wide implications on their health.

Clubbing is essentially when the angle (gap) between the fingernail bed and finger disappears. The formal definition is much more complicated, such as “the loss of the normal <165° angle, or Lovibond angle between the nailbed and the fold”, but for all intents and purposes the simple definition is sufficient.

To see if a patient has clubbing, the physician carefully studies the fingers against light. There are a few ways to check for clubbing but the most popular methods are holding the fingers out straight and holding them parallel to the ground, checking the angle between the nailbed and finger, or the Schamroth’s window test. The latter test is done by holding two opposing fingers (such as the left and right index fingers) against each other nail to nail. The fingers are then held against the light so that the light can shine through the “window” that is made. If the window is not seen, the test is positive and the patient has clubbing.

What does clubbing suggest? Clubbing was first noticed by Hippocrates, the father of Western medicine, who observed that people with clubbing tended to grab their chest and fall dead. This is one of the most common associations to clubbing – a congenital cyanotic heart defect such as tetralogy of Fallot or patent ductus arteriosus. Other common associations are related to the lungs, such as lung cancer (one of the most common causes) and various other lung diseases such as interstitial lung disease, tuberculosis and other chronic infections. There are also a myriad of other diseases associated to clubbing, including but not limited to: Crohn’s disease, ulcerative colitis, cirrhosis, celiac disease, Graves disease and certain types of cancers (lung, gastrointestinal and Hodgkin’s lymphoma mainly). Clubbing can also be idiopathic, where there is no apparent cause for the clubbing and the person just has it (possibly just born with it).

Despite knowing about clubbing for over 2000 years, we still do not know the exact reasons for clubbing. There are theories that it is related to a fall in blood oxygen content leading to vasodilation in the peripheries. As the pathophysiology is not clear and so many diseases are associated with it, when clubbing is found in the patient the physician should investigate the related organ systems (heart, lungs, GI mainly) to narrow down the possible cause of it. As many of the causes (such as lung cancer) carry a rather morbid prognosis, it is quite important to notice whether the patient has clubbing when doing a physical examination.

Posted in Science & Nature

Cordyceps sinensis

Cordyceps sinensis is a fungus known as dongchoong-hacho(동충하초, 冬蟲夏草) in Korea, with the same characters used in China and Japan. It literally translates to “worm in the winter, herb in the summer”. It is a peculiar fungus with an interesting life cycle. In the summer when the weather is warm, the fungus infects its host (usually ghost moth larvae) through spores. The infected caterpillar is slowly filled with mycelium (thready part of fungi), until it becomes mummified with only the shell remaining. The fungus keeps replicating until it bursts out of the caterpillar’s head with a club-like fruit body (which holds the fungus’ spores). This makes it look as if the caterpillar, which was an insect in the winter, turned into a fungus in the summer (technically it is at this stage, but the caterpillar is long dead). In English, it is also called caterpillar fungus or vegetable worm (which is a misnomer as fungi are not vegetables).

Cordyceps sinensis is an important ingredient in traditional Eastern medicine as it is believed to be a perfect balance between yin and yang due to it possessing both animal and plant (actually a fungus) properties. It is used to treat many diseases from fatigue to cancer.

Although Western medicine usually looks down on and ignores Eastern medicine, research shows that Cordyceps sinensis actually has medicinal properties. Cordycepin, a chemical extracted from the fungus, has been shown to inhibit the growth of viruses, fungi and tumours through its inhibitory actions on a certain protein. There is also research that suggests it can protect the body against radiation poisoning.