Declaring a pandemic

Epidemiology is the branch of medicine that handles the following:

• Incidence: the occurrence of a disease over a specified period.
• Prevalence: how many people are affected within a population.
• Control of diseases: an appropriate public health response.

Two measurable factors mostly define the level of disease occurrence:

• The pattern and speed by which a disease moves.
• The size of the susceptible population.

• Sporadic refers to a disease that occurs infrequently or irregularly.
• Cluster refers to a disease that occurs in larger numbers even though the actual number or cause may be uncertain.
• Endemic refers to the constant presence and/or general prevalence of a disease in a geographic population.
• Hyperendemic refers to persistent, high levels of disease well above what is seen in other populations.
• Epidemic refers to a sudden increase in the number of cases of a disease above what is normally expected.
• Outbreak is the same as an epidemic but is often used to describe a more limited geographic event.
• Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.

• The original use of the word Quarantine was the act of anchoring a ship arrived in Venice, Italy, for 40 days before landing.
• Infectiousness of any disease is measured by the reproduction number (R0, or R naught). For example, Smallpox has an R0 of 6 whereas Measles has an R0 of 16. 
• Vaccination, if available, and herd immunity can curb the spread of disease.
• Big cities, with exploding population and traffic, can lead to the rapid spread of any infectious disease.

The so-called Spanish flu did not originate in Spain. The geographic origin of the flu is debated to this day, though hypotheses have suggested East Asia, Europe, and even Kansas.
The influenza pandemic from 1918 got this name most likely because of the WWI context: The major countries involved in the war were keen to avoid encouraging their enemies, so reports of the extent of the flu were suppressed in Germany, Austria, France, the United Kingdom and the U.S. By contrast, neutral Spain had no need to keep the flu under wraps. That created the false impression that Spain was bearing the brunt of the disease.

The 1918 flu spread rapidly, killing 25 million people in just the first six months. This led some to fear the end of mankind and that the whole thing was caused by a form of super-virus.
Recent studies show that the high death rate can be attributed to crowding in military camps and urban environments, as well as poor nutrition and sanitation, which suffered during wartime.

The earliest recorded pandemic happened during the Peloponnesian War. It passed through Libya, Ethiopia, and Egypt,  and it reached Athens as the Spartans laid siege. Two-thirds of the population died.
The disease, suspected to have been typhoid fever, weakened the Athenians significantly and played a big role in their defeat by the Spartans.

It may have been an early appearance of smallpox that began with the Huns.
The Huns then infected the Germans, who passed it to the Romans and then returning troops spread it throughout the Roman empire.  This plague continued until about 180 A.D., claiming Emperor Marcus Aurelius as one of its victims.

Getting the worldwide economy back on track requires workforce. Providing this workforce requires healthy individuals able to work hard enough to help things get better. Governments are now trying out ways to officially have people's health checked: by providing different types of certificates, for instance. The major concern, however, is in regards to everybody's privacy: while these certificates do prove our immunity, research institutions are working on developing tools that can also protect our data.

It might be that only by certifying workers' immunity, states can help their economy know growth again. However, in order to make the people who get certified take up positions that require direct contact with customers, there will be a need for encouragement from employers' side, such as pay raises. As this is maybe the only real option, countries worldwide are going to have to apply the method.

“Save the economy or save lives” is a false choice.
A group of economists published a paper on the 1918 flu outbreak. Their findings revealed:

• Early and aggressive interventions saved lives and triggered a faster rebound, such as job growth and banking assets.
• Without a healthy population, there can be no healthy economy.

The hope is for a deep, short recession, to show that people have shut the economy down to limit the spread of disease.

Asking millions of able-bodied workers to stop working creates a crisis of unemployment.

During this time, the U.S. is expanding unemployment benefits and are also delaying tax filing. In northern-European countries, the government is directly paying businesses to maintain their payrolls to avoid mass layoffs and furloughs.

Common symptoms: coughing, fever, and shortness of breath. Non-respiratory symptoms (feeling nauseous, vomiting having diarrhea) were also reported.
The virus is more violent with the elderly, the very young and with individuals that have a weak immune system. The majority of those infected however recover after a few days.

Coughs or sneezes from an infected person are the most likely to spread the virus. So it's essential to follow basic hygiene rules:

• Wash your hand often during the day.
• Cover coughs and sneezes with your inner elbow or a napkin.
• Don't touch your eyes, nose, or mouth with your hands.
• Stay inside if you have any of the symptoms and avoid interacting with people that show signs of the infection as well.

From April 12, 2009 to April 10, 2010, CDC estimated there were 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (range: 195,086-402,719), and 12,469 deaths (range: 8868-18,306) in the United States due to the (H1N1)pdm09 virus.
Additionally, CDC estimated that 151,700-575,400 people worldwide died from (H1N1)pdm09 virus infection during the first year the virus circulated.

Though the 2009 flu pandemic primarily affected children and young and middle-aged adults, the impact of the (H1N1)pdm09 virus on the global population during the first year was less severe than that of previous pandemics.
The (H1N1)pdm09 virus was very different from H1N1 viruses that were circulating at the time of the pandemic. Few young people had any existing immunity (as detected by antibody response) to the (H1N1)pdm09 virus, but nearly one-third of people over 60 years old had antibodies against this virus, likely from exposure to an older H1N1 virus earlier in their lives.

Many scholars believe that the bubonic plague began in northwestern China, while others cite southwestern China or the steppes of Central Asia.
We do know that in 1331 an outbreak erupted in the Yuan Empire and may have hastened the end of Mongol rule over China. Three years later, the disease killed over 90 percent of the Hebei Province's population with deaths totaling over 5 million people.

From its origin at the eastern end of the Silk Road, the Black Death rode trade routes west stopping at Central Asian caravansaries and Middle Eastern trade centers and subsequently infected people all across Asia.

Compounding is exponential growth. We tend to see the immediate linear relationships in the situation, e.g., how one test diagnoses one person.

The compounding effect of that relationship means that increased testing can lead to an exponential decrease in disease transmission because one infected person can infect more than just one person.

In the absence of enough testing, we need to use probabilistic thinking to make decisions on what actions to take. Reasonable probability will impact your approach to physical distancing if you estimate the likelihood of transmission as being three people out of ten instead of one person out of one thousand.

When you have to make decisions with incomplete information, use inversion: Look at the problem backward. Ask yourself what you could do to make things worse, then avoid doing those things.