- How long could I have the virus before showing symptoms?
- How does the virus spread between people?
- How can we estimate how far coronavirus will spread?
- How does a virus that apparently started in Wuhan, China spread around the world?
- Do we know why COVID-19 is spreading so much farther compared to related viruses like SARS and MERS?
- What is the difference between coronavirus, COVID-19, and SARS-CoV-2?
- Some "social distancing" explainers — including Massive's — say "stay home." Others say that going outdoors is okay, or even beneficial, as long as people stay >10ft apart. Which is it?
- What percent of the population needs to be infected with coronavirus and recover before herd immunity kicks in?
- How does SARS-CoV-2 get into our cells and can we prevent it from doing so?
- Why are so few people infected in Russia when tens of thousands are sick in China and Europe?
- It seems like cats are also susceptible to COVID-19 but dogs aren't, is there any explanation for that?
- Will UV light, like from the sun, kill coronavirus?
- I've heard people talk about using antibiotics to treat coronavirus. Can you explain why antibiotics don’t work to treat viruses directly?
- Do we know why children are less likely to show severe symptoms?
- How can I infect others if I don't feel sick?
- If one has a normal temperature does that rule out having COVID-19?
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The incubation period of COVID-19 virus, combined with the possibility that people can possibly spread the disease without showing symptoms, partially explains how the disease spread so widely before being detected.
This incubation period between infection and symptoms allows pathogens to move stealthily across borders before being detected. It is likely that travelers passing through Wuhan were unknowingly encountering people who were infected with SARS-COV-2, the virus that causes the disease known as COVID-19. These travelers may have returned home without knowing they were infected.
Other specific features of SARS-CoV-2 can also help explain how it is making its way around the world, particularly how it moves between people and its infectiousness. We know that SARS-CoV-2 is spread through person-to-person contact and by touching surfaces or objects that has the virus on them.
The World Health Organization has officially declared this outbreak a pandemic and the public health community is continuing to work diligently to further our understanding of this novel disease and to prevent it from spreading. As such, we now must use one of our more stringent methods to slow the spread of this infectious disease and this includes limiting all unnecessary movement and gatherings, including working from home if possible, limiting unnecessary travel, and avoiding large crowds like those at concerts or sporting events.
It is time to approach our daily lives differently. While everyone can’t enact all social distancing measures, individual actions make a big difference. As always: please continue to wash your hands, refrain from touching your face, and stay home if possible. Being prepared is a great way to reduce anxiety and panic.
This is still under investigation, with new data available every day. Beyond features of virus spread, sometimes it is helpful to look at other aspects of a virus to better understand how it behaves.
The case fatality rate (CFR), which is the number of deaths from a given disease divided by the total number of people with confirmed illness, can be used as a measure of disease severity. The global fatality rate for COVID-19 was initially reported as at about 2.3%, though WHO reporting has increased this rate to 3.4%.
SARS and MERS have higher case fatality rates than COVID-19. The 2003 outbreak of SARS had a case fatality rate of around 10% (774 deaths out of 8098 cases), while MERS has killed 34% of people with the illness between 2012 and 2019 (858 deaths from 2494 cases). However, COVID-19 has lead to more total deaths because more people have been infected.
One hypothesis for the higher case fatality rates with SARS and MERS compared to COVID-19 is related to secondary infections (infections that occur during or after the initial infection). Most secondary infections from SARS and MERS occurred in hospitals, which prevented community spread of the virus. With COVID-19, we may be seeing more secondary infections and subsequent community spread as a result of primary cases not being tested, either due to lack of tests or lack of severe symptoms.
This community spread will continue as we are still having difficulties in identifying and counting mild cases of COVID-19. It currently seems COVID-19 is just as transmissible as SARS and MERS but not as deadly. However, everything we know about the virus, including R0 and case fatality rates, is preliminary and will evolve as the pandemic does.
SARS-CoV-2 is the virus responsible for the novel coronavirus disease. The World Health Organization’s (WHO) chosen name, COVID-19, is just short for "coronavirus disease" and their preferred nomenclature for the virus is "the virus responsible for COVID-19" or "the COVID-19 virus." For readability's sake, Massive often refers to the virus simply as "coronavirus."