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What you should know about COVID-19

This article will be updated regularly based on the most recent medical knowledge.

Since the start of 2020, a new respiratory infection outbreak called COVID-19 has spread through Asia to the rest of the world. This new type of coronavirus is called SARS-CoV-2.

At the beginning, the majority of COVID-19 cases were reported in China, but the outbreak is now affecting the whole world. More than 200 countries have reported COVID-19 infections, with many experiencing widespread transmission. The outbreak has been declared a pandemic by the World Health Organization (WHO) and countries have introduced measures to fight the spread of COVID-19. Do you need to be worried? What should you know about this outbreak? Our medical professionals answer some of your most frequently asked questions.


How likely is it that I’ll catch COVID-19?

COVID-19 has reached almost every country in the world. But if you aren’t in an area where COVID-19 is spreading locally, your chances of getting it are relatively low. If you are in an area with local transmission, you should take the risk seriously. Wherever you are, follow the recommended prevention measures. In either case, the situation is changing rapidly, and it’s good to keep up to date on the current situation from your local health authority.

Why do some people get more serious symptoms than others?

While people of all ages are susceptible to COVID-19 infection, four out of five have a mild to moderate illness and recover. Those over 60 years old and with pre-existing medical conditions, such as cardiovascular disease, diabetes, or high blood pressure, are more likely to become seriously ill. Children seem to be less affected.

What are the typical COVID-19 symptoms?

Typical symptoms are fever, dry cough, shortness of breath, and fatigue. But COVID-19 patients also showed less typical symptoms such as headache, generalized muscle aches and pains, sore throat, diarrhea, reduced or lost sense of smell and taste, runny nose, and red or sore eyes.

Is it possible to be infected without having symptoms?

Many people with COVID-19 don’t develop symptoms. A recent study in an affected village in Italy showed that 43.2 percent of confirmed cases didn’t develop any COVID-19 symptoms. Asymptomatic COVID-19 infections may be more common in pregnant women, with one study finding only one in ten developed symptoms following infection. Children are also often asymptomatic.

What should I do if I think I’m infected?

As the measures differ between countries, it’s important to check with your local public health authority to get advice on what to do. Before going to a doctor’s office or the emergency room, call ahead and tell them about your contacts, and symptoms, and then follow their advice. In the meantime, avoid contact with others and don’t travel. Cover your mouth and nose with a tissue or your sleeve (not your hands) when coughing or sneezing, and wash your hands often with soap and water for at least 20 seconds. Use an alcohol-based hand sanitizer if soap and water are not available. Wear a face mask to protect others.

If you are worried you may be infected, you can now use the Ada COVID-19 assessment and screener Keep in mind that further testing will be necessary to diagnose COVID-19.

Does COVID-19 cause death?

It’s possible to die from COVID-19 complications, but only a small percentage (currently 3–4 percent) of people who are infected become so unwell that they die. This means the majority of infected people recover. Mortality is higher for those over 60 years old and for those with pre-existing medical conditions.

Why are the death rates so different among countries?

If you follow the media reports, it becomes clear that the COVID-19 death rate, also known as the case fatality rate (CFR), differs a lot from country to country. In the UK and Italy, it’s around 14 percent, and in Germany or Norway, it’s below 5 percent.

There are several possible explanations. A study calculated the real number of cases by country, taking underreporting and testing capacity into account. It concluded that until the end of March, 15 percent of the Spanish population was already infected, compared to only 0.8 percent in Germany. So, the stages of the pandemic in each country seem to differ a lot. CFR might change in countries over time.

Additionally, the number of intensive care unit (ICU) beds varies a lot. Countries with lower CFR had up to three times more ICU beds per population than countries with higher CFR. Also, different testing strategies between countries impact CFR.

Is influenza a coronavirus?

No, influenza viruses are different from coronaviruses – even though they cause similar symptoms and also mainly spread through respiratory droplets.

An illustrative representation of the SARS-CoV-2 coronavirus.


How is COVID-19 transmitted?

COVID-19 transmission is similar to other respiratory viruses. It mainly spreads through small droplets that form when an infected person sneezes or coughs. Usually, these droplets only reach people (or surfaces) close to the infected person. The general rule is that droplets can spread one to two meters but not further than that. The virus does not seem to be passed through the fecal-oral route, but there is some evidence that transmission occurs through microparticles that can stay in the air after actions such as singing or loud speaking.

Is the virus only spread by sick people?

People who are not or not yet symptomatic can also spread COVID-19. Studies suggest pre- or asymptomatic transmission could be responsible for 40–60 percent of infections. It seems that people are most infectious the day before symptom onset.

How long does the virus survive on surfaces?

Early findings indicate that COVID-19 can remain on surfaces from a few hours up to several days, depending on the type of surface, temperature, and humidity. You can use a standard disinfectant to clean surfaces to prevent infection. COVID-19 doesn’t spread through letters or packages coming from an affected region.

What is the incubation period for COVID-19?

The incubation period is the time between the infection and the first onset of symptoms. The average incubation period for COVID-19 is around five to six days but can range from one to 14 days.

Can humans get COVID-19 from animals?

The origin of the virus is still unclear, but research points towards bats as the source. Until now, there are very few reports of COVID-19 in household pets (one cat and one dog) and no documentation of transmission from them to humans. Also, a tiger in a New York zoo tested positive for COVID-19, likely becoming infected through proximity to an unwell zoo employee.

How long does a person with COVID-19 remain infectious for?

There is still little available information about the duration of infectiousness. The virus can be detected for up to several weeks in samples from infected people. But that doesn’t mean the virus is active and infectious. One small study showed that the active virus was detectable in throat swabs for up to four days after symptom onset, and up to eight days in sputum samples. The active virus wasn’t detected in blood, stool, or urine. The results of this study suggested that people remain infectious for up to eight days, with reduced infectiousness after four days. These results need to be confirmed in a more extensive study.

Can I get COVID-19 more than once?

We have no long-term experiences with COVID-19 yet. Studies have shown that infected people develop antibodies, which protect them from another infection. How long this immunity lasts remains to be seen.


How can I prevent a COVID-19 infection?

Avoiding exposure to the virus is the best way to prevent infection. Standard measures to prevent the spread of respiratory viruses apply:

  • Wash your hands frequently with soap and water for at least 20 seconds. If soap and water are not available, use an alcohol-based hand sanitizer.
  • Avoid touching your eyes, nose, and mouth with unwashed hands.
  • Remain at least two meters away from anyone who has a fever and cough.
  • Stay home if you have symptoms, even mild ones.
  • Cover your cough or sneeze with a tissue and then throw the tissue in the bin.
  • Clean and disinfect frequently touched objects and surfaces.

Should I wear a mask?

Surgical or simple cloth masks are more effective at preventing infected people from spreading diseases than protecting those who aren’t sick. You can wear a mask if you have respiratory symptoms – like coughing or difficulty breathing – to limit the spread of respiratory droplets, but you don’t need a mask if you don’t have respiratory symptoms. However, some countries have recently made it mandatory to wear masks in public to decrease the spread of virus by those who might be infected. An analysis for the WHO has shown that transmission can be reduced by nearly 80 percent by wearing masks.

Medical professionals use special filter masks that are fitted to their faces and can reduce the risk of transmission. The public shouldn’t use these masks, as they are in short supply and are required to keep medical professionals safe while they care for others.


Is there a vaccine or drug for COVID-19?

There is currently no vaccine available. Vaccine production is a complicated and time-consuming process that usually takes years. In certain circumstances, like with new influenza viruses, there are established methods that can accelerate this process. That said, COVID-19 was first detected at the beginning of January 2020: Many studies are ongoing, but even in the ideal scenario, it will take several months before a vaccine is available and can be tested and used widely.

There are also many ongoing studies to test pre-existing drugs that were developed to fight other diseases such as malaria, ebola, or HIV. Tests should show if they are effective in treating COVID-19 patients. The initial results should be available soon.

COVID-19 or the common cold – how can I tell the difference?

Symptoms of the common cold and COVID-19 are very similar. That’s why understanding the significance of exposure to the virus is so important to differentiate between the two. Along with showing the typical symptoms of fever, dry cough, shortness of breath, or fatigue, people with COVID-19 have also typically been in an area where the virus is already spreading locally, or in contact with a person who has the virus.

The similarity between a cold and COVID-19 in many cases means that, for some people, the infection can seem no worse than a common cold.

How is COVID-19 diagnosed?

Infection is confirmed by testing respiratory samples in specialized laboratories. The first antibody blood tests to identify infection and possible immunity are under evaluation.


Can I go to a doctor for non-COVID-19 related complaints?

Yes. Despite the spread of COVID-19, many other diseases still need medical attention. If you are worried about your symptoms, do not hesitate to contact your healthcare professional for advice on how to seek care during the pandemic. There is evidence that people are experiencing more serious health outcomes because they delayed seeking care during the pandemic.

When will the pandemic be over?

It’s hard to say when the pandemic will be over. At the moment, there’s little indication that it will stop soon. We see decreases in the number of new cases in Europe, but at the same time cases are increasing in North and South America as well as in Africa.

What is ‘social distancing,’ and how does it ‘flatten the curve’?

Put simply, ‘social distancing’ means staying at home when you can. But the more accurate term would be ‘physical distancing’. When you do leave the house, keeping two meters away from people you don’t live with can help reduce infection.

Some countries introduced strict physical distancing measures. They closed schools, offices, bars, cafes, and shops, or only allow people to leave their house when it’s absolutely necessary.

This is helping to ‘flatten the curve,’ postponing and reducing the peak of the pandemic, resulting in fewer simultaneous cases, and ideally, fewer cases overall. During the pandemic, this limits the burden of the outbreak on health systems and helps free up ICUs for the most serious cases.

Slower acceleration in number of cases = Reduced peak in number of cases and demand on healthcare infrastructure

Are the measures working?

To judge if the measures are working we have to look at how we can assess their success. One important indicator is the reproduction number (R0) of an infectious disease. This number describes how many people are infected on average by one person. The R0 can be up to 18 for measles, which is the most contagious known disease. Seasonal influenza tipically has an R0 of one to two. The R0 is affected by immunity in the population (including available vaccinations), transmission routes, and control measures. Without control measures, the COVID-19 R0 was estimated to be three to four. This resulted in the exponential growth of infections in the beginning.

Epidemiologists use R₀, which stands for reproduction number, to indicate the average number of people that one person will infect. Here are the R₀ values for five viruses: Seasonal influenza 1-2, Ebola 1.5-2.5, COVID-19 3-5, Chickenpox 10-12, Measles 12-18

With the control measures of physical distancing, the estimated COVID-19 R0 in many countries is around one now. This shows that the measures were effective and that we have flattened the curve. Countries are slowly lifting these measures, closely monitoring the effect on transmission rates.

We all need to respect our local health authority’s control measures during the pandemic to help keep infection rates low and avoid an increase in the number of infections again.


Dr. Andreas Gilsdorf

Andreas is Ada's Director of Epidemiology and Public Health.