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What is contact tracing of Coronavirus

ECONOMYNEXT – Contact tracing combined with isolation and quick testing has been use to stop the progress of Coronavirus in several countries in Asia, with major progress being made when it was used early in the Covid-19 crisis.

Vietnam and Sri Lanka are among countries in the world that have used contact tracing and quarantine most effectively to stop the progress of Coronavirus.

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How Sri Lanka and Vietnam are smashing Coronavirus, and what will happen next
How Sri Lanka and Vietnam are smashing Coronavirus, and what will happen next

Once an index case is found, contacts of the person is located, isolated/quarantined and tested. The contacts of contacts are also tested.

Vietnam and Sri Lanka has confined total cases found to a few hundred but there may be more out in the country.

For a crash course in contact tracing Coronavirus index cases and how to test contacts read this fast-tracked article at International Journal of Tuberculosis and Lung Disease (IJTLD)

Contact tracing is an old tactic used by health services to fight epidemics spread by human-to-human contact ranging from Tuberculosis to Ebola.

Unlike TB, Coronavirus spreads very fast, so contact tracing has to be quick. Unlike Ebola there is no fever in all patients so contacts have to be tested fast to find whether it has infected the next level of contacts.

Since contacts expand exponentially (community transmission) the disease can quickly get out of control.

Nigeria used contact tracing against Ebola very successfully from the index case Patrick Sawyer which was recognized as world-class epidemiological detective work.

But unlike Ebola where symptoms come up fast Coronavirus has asymptomatic cases.

When community transmission is widespread it is difficult to trace patients back or forward. Whe public services collapse once community transmission takes place all efforts are put to mitigation.

A person who comes from abroad carrying the virus (or the person who got the diseases in Wuhan supposedly from an animal) is the index case or F0. The contacts of F0 are F1. The contacts of F1 are F2. Contacts of F2 and F3.

In Sri Lanka they are called Fist Ring, Second Ring, Third Ring.

If there is cluster of several levels, the entire area is surgically locked down until all contacts are identified or incubation period passes and they are tested. But there is evidence that some people get infected as late as three weeks after contact.

Sri Lanka has extended quarantine to three weeks.

Researchers from Woolcock Institute of Medical Research, Hanoi, Viet Nam; Sydney School of Medicine, The University of Sydney, Australia including T A Nguyen, Q N Cuong, A L T Kim, T N Huong, H N Nguyen, G J Fox, G B Marks, have shown in a recent publication how contact tracing should be combined with testing of contacts of index cases to quickly stop the spread of virus.

“First, three generations of contact (F) with COVID-19 cases should be traced to offer timely testing if the previous contact generation is found positive,” the researchers say in the fast-tracked paper in the International Journal of Tuberculosis and Lung Disease.

“All F1 contacts should be tested for SARS-CoV-2 regardless of symptom presentation.

“F1 individuals who are asymptomatic or have two negative tests 24 hours apart should be quarantined for 14 days.”

“F2 contacts should self-isolate at home and be monitored by public health units. If F1 tests positive, we recommend that F3 contacts should also be identified. When the previous F becomes positive, the next one will be informed to follow the contact management procedure.”

Contact tracing flow diagram drawn TA Nguyen et al.

Because it is believed that persons develop the disease as closely as two days, Coronavirus can spread rapidly to the next level. But if they are traced quickly and the levels identified the expanding line of transmission or cluster can be stopped.

All quarantined persons should also be tested before at least twice according to the process followed y by Sri Lanka and almost from the beginning in Vietnam.

To be successful, contact tracing has to start early, when foreign returnees first start coming. The later arrivals are blocked, the more difficult it is to contain community transmission.

Sri Lanka and Vietnam both quarantined and effectively killed the Wave I from China from all available evidence.

Sri Lanka found one patient from Hubei province in China. Vietnam found 16 during January and February 2020.

Wave I is the infection that spread from China to third countries. Any country that restricted arrivals from China, quarantined those that came, and stopped community transmission from Wave I, also stopped the of export of their citizens with Coronavirus to third countries.

Wave II is the pandemic where third countries came back to infect a country. Researchers are now thinking that the SARS-CoV-2 virus may be as old as September 2019.

Any country that allowed returnees to come from China without quarantine (either Chinese or their own citizens) let community transmission to take place in the Wave I epidemic. They then re-exported their citizens to contribute to the Wave II pandemic.

Sri Lanka and Vietnam closed airports for inbound traffic as quarantine became full endangering the contact tracing and isolation process as systems got overwhelmed.

They tightened border controls against the advice given by the WHO at the time.

Read: Updated WHO recommendations for international traffic in relation to COVID-19 outbreak

Both countries also stopped the Wave I from China with minimum controls against China, stopped community transmission and did not contribute to the pandemic that followed by exporting their citizens as far as is know.

It raises questions about exiting strategies followed in not quarantining all arrivals when unknown diseases are found. (Colombo/Apr18/2020)