The virus is spreading as a disease (so far over 90,000 people infected and over 3,000 dead) but is also spreading a lot of confusion.
As a pathogen (a cause of disease), COVID19 seems to spread from person-to-person when people are in close contact with one another (about 6 feet or 2 meters apart) and through droplets from an infected person (from coughing or sneezing). These droplets only travel about 3 feet (a meter) before they land on people’s mouths, eyes, or noses or on surfaces from which they can be “picked up.”
As a source of confusion, COVID19 generates uncertainty because people are unsure of how a virus works and what constitutes cause for alarm.
Pathogens
A pathogen is a disease-producing agent that may or may not be foreign to the body. We normally live with trillions (as in 1014 or 100 000 000 000 000) of non-human creatures in our body. Most are bacteria and make up our normal flora, non-human cells that we do not only live with but live by.
Sometimes, if our immune system is weakened, normal flora can cause trouble, and also pathogens which are not part of our normal flora will sneak in and cause trouble. Here’s where viruses come in.
Each individual pathogen causes disease in a different way. Bacterial pathogens, which are single cell organisms, carry specialized virulence (hostility) genes, but can be treated with antibiotics. Fungi and protozoan parasites are multi-cellular organisms that are harder to treat than bacteria.
Viruses are not even cells. They are made up of a single nucleic acid type—either DNA or RNA that makes up their genome (their biological mold). Nucleic acids are the alphabet and engine of life: they store genetic information and enable protein production. And proteins are, quite literally, the building blocks of life).
Some viruses exist more “naked” than others. Their genome can be protected by a single protein coat (capsid) or further wrapped in a fatty coat (lipid bilayer).
There is another form of infectious pathogen, smaller and rarer than viruses called prions. They are evil twins of regular proteins with a deformed structure that can bully other proteins to deform. An example of this is the Mad Cow Disease (Bovine Spongiform Encephalopathy).
How Viruses Work
Viruses are protein machines. While they come in a wide variety of shapes and sizes, they all consistently make three types of proteins. Viruses make proteins for reproduction that essentially make copies of the virus, proteins for packaging the virus and delivering it to other host cells, and proteins that modify the structure or function of the host cell.
While bacteria, fungi, and protozoan parasites have in common have their own machinery for nutrition and reproduction within their cells, viruses are absolute free-riders. They use the nutrition and reproduction machinery of their hosts. They act as an uninvited guest who raids and ransacks your kitchen leaving a trail of destruction as they move on to your neighbors’ kitchen.
A single virus particle (a virion) that infects a single host cell can produce thousands of offspring. These offspring either end up killing the cell by bursting out of it (a process called lysis) or turning the cell against itself through chronic infection (long lasting) or cancer. Multiply that by the many cells they attack… and we have a big problem.
Vaccines
Vaccines are dead or inactivated pathogens or products derived from them that prompt a beneficial immune response. Some inactivated vaccines include vaccines against polio, hepatitis A, rabies and some influenzas. Some attenuated (tamed pathogens) vaccines include vaccines against yellow fever, measles, mumps, and rubella. Vaccines for tetanus and diphtheria use inactivated toxic compounds. Subunit vaccines use a fragment from a pathogen to promote the immune response, like the vaccines against Hepatitis B and the human papillomavirus (HPV). Last, but not least, conjugate vaccines combine weka and strong antigens (chemicals that prompt the body to fight infection) so that the body remembers to react to the weak ones, as in the vaccine for Haemophilus influenzae type B.
Levels of Spread
Diseases spread. After all, pathogens—like all living things—are programmed for survival. Sometimes, disease even helps restore balance to an ecosystem.
But how far and fast disease spreads can be very concerning not just to humans but for all hosts harmed in their path.
Let’s talk about “demics”: epidemic, pandemic, endemic. We often use these words interchangeably to talk about the spread of disease. And, sometimes, we even use it to describe behaviors, as in “There is an epidemic of bullying in schools.”
When disease strikes, epidemiologists study the incidence (when and where disease happens), prevalence (proportion of people affected), and containment (treatment and control) of diseases. Based on the two first factors diseases can be:
- Sporadic: the disease is not frequent, such as foodborne illness like Salmonella or E. coli.
- Clustered: the disease appears temporarily as bunch of cases in one area, for example, cancer cases after a chemical or nuclear spill, or contamination like the lead incident in Flint, Michigan from using a corrosive water source.
- Endemic: the disease is constantly present in an area or population, but in relatively low frequency. When the disease is constantly present but in high levels when compared to happens in other populations, it becomes hyperendemic. For example, HIV is endemic in the US (1 in 300 people infected) but hyperendemic in Africa (6 in 300).
- Epidemic: a disease suddenly spikes, that is, the number of cases grows rapidly and above what is normally expected. If the epidemic is clustered, that is, the disease suddenly spikes but is limited to a geographic area, it is called an outbreak. For example, the Zika outbreak of 2016 was limited to warm climate areas in the Americas (including the Southern US).
- Pandemic: this is an epidemic that has spread over several countries or continents, usually affecting large numbers of people. HIV was a pandemic (between 2005 and 2012) and has infected over 75 million people worldwide; currently 35 million people around the world are infected (about 21 million people in Sub-Saharan Africa, which amounts to 5% of the African population).
Past and Current Pandemics
In addition to HIV, many diseases have caused, and continue to cause pandemics.
Influenza pandemics have occurred more than once: in 1918, influenza killed 40-50 million, in 1957 it killed 2 million and in 1968, 1 million. Asian influenza killed 2 million people in 1957.
Tuberculosis is an ongoing pandemic that kills over 1.5 million people every year.
Malaria, despite being a preventable disease is almost at the level of a pandemic, killing ½ million people every year.
The smallpox pandemic in the 20th century killed almost 500 million poeple. Edward Jenner in 1798 confirmed that cowpox provided protection against smallpox, but it wasn’t until 1959, that a global eradication effort was launched. The World Health Organization (WHO) launched a huge campaign and in 1980 smallpox was declared eradicated and continues to be the only human disease eradicated to date.
The Black plague killed more than 75 million people from 1347 to 1351. And even after, the plague continued to strike Europe, the Middle East and beyond for centuries, returning every 10 to 20 years. The plague had wreaked havoc before, when it was called the Plague of Justinian, striking Europe in 541 CE and killing 50 million people in one year, which amounted to half the continent’s population at the time.
(A note on plague: this is not an epidemiologic term. It refers to a contagious bacterial disease characterized by fever and delirium, such as bubonic plague.)
Phases of a Pandemic
The WHO has articulated phases of a pandemic to help people and governments prepare and respond to disease spread. The phases are based on the spread of influenza and designed to address viruses that jump from animals to humans.
- Phase 1: no animal viruses are reported to cause infection in humans.
- Phase 2: first level of threat; a virus is confirmed to have jumped from an animal to humans.
- Phase 3: sporadic cases or small clusters happen, but human-to-human transmission has either not occurred or hasn’t gained a level of transmission that can cause a pandemic (human-to-human transmission may occur in close contact).
- Phase 4: human-to-human transmission happens easily or animanl-to-human transmission has caused a community-wide outbreak.
- Phase 5: human-to-human transmission of the virus has caused the spread of disease to at least two countries in a WHO region.
- Phase 6: the disease is declared a pandemic. It has spread to at least one other country outside a single WHO region.
The duration of each phase can vary and be influenced by weather, climate, response, or the virus spontaneously weakening.
Is COVID-19 a Pandemic?
The causes for concern include that fact that the virus can kill healthy adults in addition to sick elderly people, and that it can spread at an exponential rate (an infected person, even before symptoms, can spread the disease to several other people).
A study on data from China‘s Infectious Disease Information System suggests the virus can kill 1 of every 100 infected; this is a higher rate than the flu.
On this one, I agree with Bill Gates, who recently wrote, “Covid-19 has started behaving a lot like the once-in-a-century pathogen we’ve been worried about. I hope it’s not that bad, but we should assume it will be until we know otherwise.”
