What is contact tracing and why is it so effective in stopping COVID-19?


WHO talks about finding contacts at each press briefing. They constantly emphasize that contact tracing is the key to removing COVID-19 and then stopping it. They say tracking contacts will not only delay the spike, but will delete it and overwrite it with no new cases a day.

For some reason, some countries ignore this advice. I wonder if this is partly due to the fact that few people realize what it involves and why it is so effective for this disease? This does not mean following random people as you pass by in supermarkets or on the street. These are close or prolonged contacts.

It wouldn’t work the same way for the flu, or even for SARS. It works for Ebola and has been the key to suppressing and stopping Ebola. It also works, surprisingly, for COVID-19, which is a rather unusual respiratory disease.

What is contact tracking?

This graph helps explain what it is and why it is so effective. Contacts are often members of the same household or close contacts who know each other well. This makes isolation much easier than for most diseases. Simply isolating the cases from their own homes had the potential to stop 75% to 85% of transmission in China.

This is a British Medical Journal article calling on government to resume contact tracing

Case finding, contact tracing and screening, and strict quarantine are classic public health tools for controlling infectious diseases. The WHO says they have been carefully adopted in China, with a high percentage of identified close contacts having completed medical observation.
In Singapore, Vietnam and South Korea, careful contact monitoring combined with clinical observation and testing was essential to contain the disease. This, combined with strong measures to enforce the isolation of travelers returning from high-incidence areas, has avoided the need for a national lockdown and the closure of all schools in Taiwan and Singapore.
The mathematical model used by the British government clearly shows that a rigorous contact search and case search are effective: the prediction of 250,000 deaths was based on what would happen without the contact search.
The reasons why the tracing was stopped, contrary to WHO recommendations, have not been published. It appears to be linked to a shift from “contain” to “delay” in the government’s plan of action, when contact tracing has been replaced rather than supplemented by other control measures.
Covid-19: Why is the British government ignoring WHO advice?

Covid-19 is an infection over a very long period of time, ranging from several days before symptoms to two weeks after symptoms disappear. For more details, see

WHO monitors scientific reports and has found no evidence that COVID-19 is airborne, with the exception of certain medical procedures – unlike SARS, which was shown to be airborne from the start . It only transmits through the larger droplets that fall to the ground in seconds, when you cough, sneeze or speak.

COVID-19 is usually passed to other members of the same household or to contacts with whom you are in close or very prolonged contact. He also does it slowly. One person will only infect one in ten contacts, even in the same house

The top priority is to isolate people from the same household. In China, 75% to 85% of transmission took place in households. Stopping this alone is enough to have a significant effect on the removal of this virus.

Most of the rest is passed on to people the case knows or who are easy to trace.

Cases don’t usually infect others on the street, in an elevator, or in a supermarket. It is much more normal to infect other people in a clinic, hospital, cruise ship, prison or your close work colleagues. Either you know them well, or someone else has arranged to meet you and the organizers are able to find them.

This is why contact tracking is so effective for COVID-19. The contacts that you can identify relatively quickly by speaking to the patient are the most important to isolate.

Then, the long incubation period of up to 14 days and the long infectious period mean that even if you find contact several days after they become infectious, you still effectively reduce the spread.

For all these reasons, if you immediately isolate all contacts from a case as soon as you find it, you greatly reduce the spread of this virus. It’s not just theoretical, South Korea, China and others have shown it by doing it.


Text: South Korea has increased its cases ten times a day in two weeks
We can too
Many of his remaining cases are imported from other countries.

It was the same for China

Text: China reduced number of cases per day by 10 times in two weeks
We can too
You see the effect of the measures until a fortnight later due to the time taken from infection to symptoms and then to diagnosis.

Once we have come up with a smaller number of cases, then all we need to do is isolate these, not society as a whole and the lockdown may end soon, perhaps as early as 4 next few weeks or so (we would notice the effects after 2 weeks, and after 4 weeks we would have significant reductions)

Spain and Italy did the same.

The UK cannot expect to follow the same path as Italy and Spain if they only do physical distance and do not do case finding and contact finding.

Italy and Spain are seeing cases a day and now even the deaths are falling, but they have tested all the mild cases and isolated them, traced the contacts and quarantined the contacts. They also protected their health systems.

We have to do the whole package, not just locking and testing, if we are to be successful like other countries have done.

This is another article I write to support the people we help in the Doomsday Debunked Facebook group, who find us because they are afraid, sometimes to the point of committing suicide, about such stories.

Please share this widely and most importantly, let’s try to get the attention of policy makers in the UK, as well as journalists and experts who may have the ear of politicians.


WHO publishes a series of technical documents to guide governments. See national and technical guidelines – Coronavirus disease (COVID-19).

WHO currently recommends quarantining all contacts, whether or not they have symptoms, to catch them in the presymptomatic stages. If they develop symptoms, they are then tested and if necessary, isolated as new cases and the process begins again

All contact must be placed in quarantine for 14 days from the last exposure to the patient.

They count as exposed if they have done so, from 2 days before and up to 14 days after the onset of symptoms in the patient:


You can completely overwrite COVID19. China and South Korea have shown how. Spain and Italy are doing it now too. The WHO says it at every press point, but the media hardly ever talks about it. To do this, you test, isolate and take care of cases, trace the contacts and put the contacts in quarantine.

You don’t need to find everyone.

If you stop 75% of transmissions, you change a transmission that will

100 cases → 200 cases → 400 cases

to whoever goes

100 cases → 50 cases → 25 cases

and it will stop soon.

Even if you have a million cases, you can get a reduction of ten times a fortnight with rigorous contact tracking. It can go down as fast as it has gone up.


With all the locks, we have a second precious window to find the confirmed cases and isolate them and quarantine all their contacts.

Like Maria van Kerkhove said at the WHO press conference on March 30:

Maria van Kerkhove: In a sense, the transmission was removed from the streets and returned to family units. Now we have to go to the families to find these people who can be sick and remove them and isolate them in a safe and dignified manner, as I said before; the transition from movement restrictions to closings and residence orders can only be made if we have the means in place to be able to detect suspicious cases, isolate confirmed cases, follow contacts and monitor the health of contacts at at any time, then isolate all the people who fall sick themselves.
COVID-19-virtual press conference -30 March 2020

It’s possible. If we do, the cases per day will decrease rapidly. This is a golden opportunity to do so. We have a lot less contacts during a lockout, which makes it easier to track contacts.

We also have millions of isolated people at home who are unable to work and could help track contacts as volunteers.

The isolation must be long enough – and isolated from other members of the same household.

The managing director said so in his famous “test test test” speech, where the UK only spoke of the need for a lot of testing and left out the need to isolate confirmed cases.

Caring for infected people at home can put other people in the same household at risk, so it is essential that caregivers follow WHO guidelines on how to provide care in the safest way possible.
For example, the patient and their caregiver should wear a medical mask when they are together in the same room. [point 3]

People infected with COVID-19 can still infect others after they stop feeling sick, so these measures should continue for at least two weeks after the symptoms disappear. [point 4]
Visitors should not be allowed until the end of this period.
Opening address by the Director-General of WHO at the press conference on COVID-19 – March 16, 2020
Tips detailed here: Home care for COVID-19 patients with mild symptoms and management of their conta

If we get a second wave – then we do the same thing again but we catch it much faster at an earlier stage.

When we reach the top and the daily cases start to drop, the message is to continue our efforts and push it to zero. Then keep the alert and keep it at zero if it reappears.

This is not possible with the flu, but COVID-19 is a very unusual respiratory disease, also different from SARS which was airborne, and COVID-19 can be stopped this way.

From this same press conference:

Mike Ryan: The question is how to get in and out is not just about locking and letting go. To come down with numbers, not just to stabilize, we need to redouble our public health efforts to bring them down. It will not descend by itself. It will be rejected and that is what we need to focus on on the countries.
What is the strategy to put in place now, the public health measures that will roll back the virus after the publication of these measures, then how to take better care of people in a clinical environment to save more lives
Maria van Kerkhove: These physical distance measures, these home maintenance measures have saved us a little time, a small window of time and this short window must be used appropriately so that we put systems in place to search for this virus. aggressively through testing. , by isolation, by searching for contacts, by quarantining these contacts, by taking care of new patients, because we will always see patients and many patients will still need needs, to support other countries that will pass by there.
So focusing on what we are doing now is absolutely essential to make sure we are using this time wisely, we are using this time effectively so that once we reach this peak we continue to grow back and remove this virus as soon as possible but always ready to find additional cases if they arise. What we have seen in a number of countries in Asia where they have brought down this virus, they have lowered this transmission; they now see repeated introductions from outside their country. They have not let their guard down, they are still looking for these cases aggressively on arrival and removing them so that it does not start again.
So we have to focus on it now, we have to use our time wisely and that is to aggressively find this virus and take care of our patients
COVID-19-virtual press conference -30 March 2020

The video of this press conference is here.

The WHO has been saying this at every press point for weeks.

It is so important and yet so many countries do not seem to understand its importance.

See my

This is from my most

See also


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