By Alex Crawford, special correspondent

They are sleuths to be reckoned with.

Thousands of track and trace teams fan out across Turkey every day and night hunting down patients struck down by coronavirus and all those people they’ve been in contact with for the previous fortnight.

Much of the country's success in containing the disease has been put down to Turkey’s so-called COVID-19 "detectives".

Two members of Turkey's track and trace team kitted out to visit the home of someone who needs to be tested

Two members of Turkey's track and trace team kitted out to visit the home of someone who needs to be tested

Turkey has managed to test millions of people for the virus and has registered more recoveries from the disease than infections for the past four weeks on the trot.

One of the country's leading doctors told Sky News that Turkey's relatively low mortality rate is down to the extensive testing and tracing network, as well as aggressive treatment in the early stages of the disease.

Professor Nurettin Yiyit said the Turkish administration has also been manufacturing and administering its own hydroxychloroquine drug, controversially endorsed by US President Donald Trump.

Turkey has been using hydroxychloroquine, which has been controversially recommended by Donald Trump

Turkey has been using hydroxychloroquine, which has been controversially recommended by Donald Trump

They have had dramatically good results, although they employ multiple treatment disciplines - including giving plasma from recovered COVID patients - and are now using the anti-viral favoured first by China called favipiravir.

The official number of COVID-19 deaths in the country is under 6,000 in a population of 83 million – this compares with the UK's 46,000 deaths, despite having a smaller population of 66 million.

There are about 8,500 tracer teams made up of 16,300 "detectives".

Every contact of every person who tests positive is found by the COVID 'detectives'

Every contact of every person who tests positive is found by the COVID 'detectives'

Every child, relative, acquaintance, workmate and secret lover of every person who tests positive is found and told to isolate for 14 days.

They are regularly followed up by health workers and tested as soon as they begin to show symptoms, and their treatment starts early even if symptoms are very mild.

The health workers test as soon as symptoms begin to show

The health workers test as soon as symptoms begin to show

Every part of their treatment, from testing, medicines and hospital treatment, is free.

Fatih is just one of Istanbul's 39 districts each with its own network of tracers.

During the day in Fatih, there are an estimated 4.5 million people passing through, working or visiting.

Dr Melek Nur Asla, who is director of the Istanbul Fatih District Health Directorate, has 40 teams on the go under her command in Fatih, which encompasses Turkey's famous Blue Mosque, Hagia Sophia mosque and internationally-renowned Grand Bazaar.

Dr Melek, who works in Istanbul's Fatih district, has 40 teams under her command

Dr Melek, who works in Istanbul's Fatih district, has 40 teams under her command

She has a 24-hour telephone hotline running with a string of linguists ready to question every caller thoroughly and prompt them to remember every single person they've been in contact with the previous fortnight.

"We don't want them to lie to us," says Dr Melek.

"Often we make them remember people, locations, instances they have just completely forgotten. We are truly like detectives."

Istanbul is Europe's most populated city with about 15 million residents living in one of the most crowded areas of the Western world.

Fatih encompasses some of Istanbul's busiest areas, including the famous Blue Mosque, Hagia Sophia, street markets and Grand Bazaar

Fatih encompasses some of Istanbul's busiest areas, including the famous Blue Mosque, Hagia Sophia, street markets and Grand Bazaar

To put it in context, Turkey's albeit smaller neighbour Greece has a total population of under 11 million.

At the peak of the pandemic, Istanbul was the country's epicentre. But test and trace teams started work immediately when the first COVID-19 patient was diagnosed on 11 March.

"We started straight away," Dr Melek says. "We had the teams all in place already and the plans all there. We just had to dust off them off and put them into action. And we haven't stopped.

Dr Melek says her team have been working long hours to bring COVID-19 under control

Dr Melek says her team have been working long hours to bring COVID-19 under control

"None of us could live with ourselves if we missed a single person or someone died because we didn't trace them. We have been working all hours."

Dr Melek is "100% sure" her team in Fatih has traced every single coronavirus patient as well as all the people they were in contact with from the start of the pandemic in Turkey – an astonishing claim, but one she insists she is certain about.

The rigorous testing (4.7 million tests and counting to date) has enabled Turkey to stay one step ahead of the virus, according to Dr Yiyit.

He runs three large hospitals in Istanbul, including a deluxe one built in a record 45 days specifically for pandemic patients.

Professor Nurettin Yiyit is in charge of three large hospitals

Professor Nurettin Yiyit is in charge of three large hospitals

The hospital, known as the Professor Fariha Oz Emergency Hospital, covers a huge 75,000 square metre area on the Asian side of the city, with 1,008 beds - of which 432 are intensive care (ICU) beds. All of them can be turned into ICU beds if necessary.

Each patient admitted has an individual room equipped with a TV, telephone and camera for constant medical observation, and a negative pressure system to hoover the virus out.

The ICU rooms also have a double-door system where one door has to close before the second opens to enforce non-contamination.

The Professor Fariha Oz Emergency Hospital, on the Asian side, covers a huge 75,000 sq metre area

The Professor Fariha Oz Emergency Hospital, on the Asian side, covers a huge 75,000 sq metre area

Like many of the doctors we've interviewed across the world, the Turkish medics also discovered early on in the pandemic that success lies in catching the disease early on in its progression and avoiding the use of ventilators unless as a last resort.

Dr Yiyit says: "Our target is to be ahead of the virus… all of us aim to stop the progression of the disease. To treat the disease is hard. The best way is to stop the progression of the disease."

And they are doing that aggressively.

The Turkish medical teams believe that success lies in catching the disease early

The Turkish medical teams believe that success lies in catching the disease early

As soon as a patient has symptoms, they are treated with hydroxychloroquine tablets and/or favipiravir at home.

Follow-up calls quickly spot if the symptoms worsen, and then they will be admitted to hospital.

Once at the hospital, Dr Yiyit says the treatment is increased and combined with high-flow oxygen treatment, anti-coagulants, steroids, vitamins and more high-dose favipiravir or hydroxychloroquine.

Most patients leave within days.

Doctors in Turkey are tackling coronavirus aggressively, using techniques like computed tomography to spot the signs of severe illness

Doctors in Turkey are tackling coronavirus aggressively, using techniques like computed tomography to spot the signs of severe illness

"Most of patients recover in five days," Dr Yiyit insists.

"Generally we follow up all the patients for two weeks after that. After two weeks, if he or she has no symptoms, we stop the follow-up and they are deemed to have recovered."

The more serious ones tend to come in late for treatment, he says. Then it becomes increasingly difficult.

Sky News saw a few patients on ventilators in the ICU and at least one was being given immune plasma to try to help recovery.

Among the therapies is the use of blood plasma from recovered patients

Among the therapies is the use of blood plasma from recovered patients

"The plasma is like a vaccine," Dr Yiyit says. "But it does not work on everybody and it's better to have it, again, at the beginning of the disease.

"There is still a lot we do not know about this disease. We are all still learning. But it is most important to stay ahead of the virus."