The Covid-19 epidemic began in December 2019 and spread rapidly. By now, there are more than 105 thousand cases in more than 100 countries and territories. How can a virus spread that fast in less than four months?
Most of the answer lies in the properties of the virus and the ease of transportation.
1. Asymptomatic Carriers
A carrier is someones who harbors an infectious microbe. A carrier may be sick and have symptoms like fever, coughing, or runny nose. The asymptomatic carrier has none.
Two other coronaviruses, the SARS and MERS, have caused an epidemic in 2003 and 2012, respectively.
The difference is that the SARS and MERS spread only when they become symptomatic. Once they have symptoms, they can be tested, identified, and isolated. The carriers were easily contained
That is why the SARS and the MERS did not cause an epidemic as widespread as the Covid-19.
Having symptoms have two consequences, the sick person may elect to stay at home and limit the spread to others. He may also feel bad enough that he will seek medical attention and get diagnosed, treated, and isolated.
On the other hand, the asymptomatic carrier goes about his daily life. He can go anywhere. Since he is not sick, people are comfortable associating with him. In the meantime, he is spreading the virus to all his close contacts.
The virus spreads by droplets from coughing or sneezing and contaminated hands.
2. Long Incubation Period
The incubation period is the time when a person gets the virus to the time the symptoms start. Seasonal influenza has an incubation period of 2 days. Once you get exposed to the flu, you will have the symptoms in 2 days.
For Covid-19, the incubation period is from 7 to 14 days. Within that incubation period of the asymptomatic carrier can spread the infection to his family, workplace, restaurants, gyms, movie houses, and place of worship. Imagine the number of people you get in contact with every day.
3. The Mild Symptoms of Covid-19 Mimic many conditions
Mild cases of Covid-19 are seen in about 80%. Those symptoms can be a runny nose, diarrhea, a sneeze, a cough, or a slight fever. Those symptoms are similar to allergies or the typical run of the mill viral infection.
If the symptoms are mild, the tendency can either be to ignore it or take over the counter medications or sleep it off.
If ever they present to a physician, they can easily get misdiagnosed, especially if there are no known cases around that area.
More so, no one will call off work or be allowed to absent themselves from school or work if the symptoms sound like “allergies” only.
No one will postpone their paid-for cruise or international trip just because of a mild “cold” that will “go away soon” once you get that “fresh air.”
Another reason is, if the symptoms are mild, there will probably be a lot of hesitation in seeking medical attention, especially if there is a $50 copay. Others may have no primary doctor and have no insurance and would not want to be billed thousands of dollars for a single emergency room visit for something mild.
4. The Hard Shell of the Covid-19
The Covid-19 has a shell. A recent article I wrote, New Study Explains the Rapid Spread of Covid-19, talks about a study that analyzed the protein structure of the shell of Covid-19.
The shell of Covid-19 is stable enough to survive the acidic environment of the stomach and the digestive juices of the intestines. That means they not only survive but also multiply in the gut.
Once they pass in the feces, they can contaminate the hands. Effective hand washing takes at least 20 seconds. That’s about the time it takes to sing “Happy Birthday” unhurriedly.
Next time you go to the bathroom, time yourself. Better yet, once you are in a public restroom, time other people as they wash their hands. Just don’t sing the Happy Birthday song out loud. That will be weird.
Contaminated hands contaminate. The hard shell of the Covid-19 also allows it to survive in smooth surfaces for as long as 9 days. Anyone touching that surface during that time is at risk of getting the virus.
Therefore, the Covid-19 not only spreads by the droplet but also fecal-orally.
5. Ease of Travel
Traveling nowadays is so easy. Wuhan is a city in China where the epidemic started. I wrote about it in To Know What’s in Wuhan is to Know Why Coronavirus is a Concern.
Wuhan is a city of 11 million people and is a transport hub. There is an international airport with 6 flights going to Europe every day. A bullet train that can do to HongKong in 6 hours and Shanghai in 4 hours. Expressways and highways crisscross Wuhan. And since it is in the middle of China, anyone can go anywhere in China quickly. There is also a shopping port.
The first two Covid-19 cases in Italy came from Wuhan. Now, Italy has 5,883 cases.
Qom, Iran, is a pilgrimage site for Shiite Muslims. Millions travel there a year. Most of the Covid-19 patients in the middle east came back from Iran.
Now that we know how and what makes the virus spread, how infectious is it in numerical terms?
Two Measures of Infectivity
1. R nought, R0 (pronounced R-nort)
Ro nought is the number of people that 1 person can transmit the infection to. Covid-19 has an R0 of 2.2. That means from one person, it can spread to more than 2 people.
2. The secondary attack rate (SAR)
In The Secondary Attack Rate of Covid-19, I presented a study that showed the Secondary Attack rate is 35%. The secondary attack rate is the ratio of people who are close contacts of an infected person who will get the virus. Provided there is enough time that they are together.
An example is, if an infected person gets in contact with 3 people, then 1 gets infected. If that person gets in touch with 15 people, then 5 will become infected.
If it looks like it is much different than the R nought, it is. I think the spread of Covid-19 is closer to the value of the SAR than R nought.
Putting it all together
Someone who is an asymptomatic carrier of Covid-19 can travel anywhere and even internationally for two weeks. During that time, he can spread millions of viruses by droplets and contaminate everything he touches.
Those viruses can then survive for 9 days and contaminate many more.
That is why avoiding touching the face, and proper hand-washing is critical now more than ever.
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Don’t Get Sick!
Related Readings:
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- Covid-19: Why Should Health Care Workers be Protected?
- The Covid-19 can Attack the Brain
- New Study Explains the Rapid Spread of Covid-19
- 6 Disinfectants against the Coronavirus
- 5 Disinfectants for Coronavirus You May not Know
- What Happens to Critically-ill Covid-19 patients?
- 6 Ways Exercise Protects against Infections
- Not enough U.S. hospital beds once Covid-19 epidemic is full-blown
- Is the Covid-19 epidemic Fake News?
- Covid-19 Can Cause Drugs and Medical Supply Shortages Worldwide
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