Turning the tide of COVID-19

The number of people known to have been infected worldwide with SARS-CoV-2 has soared past three million and claimed the lives of more than 200,000.1 And the number of known cases continues to rise − it can now be found on every continent except Antarctica.2

The United States has had the greatest number of confirmed cases − and deaths – exceeding even the toll in China where the disease originated. However, public health experts have voiced their concern that the current number of both cases and deaths is inaccurate because too few people have been tested. While the virus is deadly for some, causing pneumonia, severe acute respiratory syndrome or kidney failure, many who have it experience mild symptoms or no symptoms at all, making it much harder to detect and contain.

In every country affected by the pandemic, experts have come to recognise one indisputable fact: accurate, high-volume testing is critical to containing and controlling this global health threat. Along with measures like social distancing and self-isolation, high-quality testing is an essential part of the response to the COVID-19 pandemic, which currently has no approved vaccine or disease-specific treatment.

Medical researchers and health system authorities have been collaborating closely to ensure that tests are developed, reviewed and made available to as many people in as many countries as possible. The tests also need to ensure that the samples can be handled safely and not contaminate the testing equipment or put laboratory staff themselves at increased risk of catching the disease.

Currently, there are two types of tests providing the most essential information about infection with SARS-CoV-2 – a molecular reverse transcription polymerase chain reaction (RT-PCR) based on a patient’s nasal sample and an antibody test based on a blood sample.

While molecular testing helps identify people with an acute viral infection, antibody tests can tell whether a person has been infected and potentially developed immunity to the virus, including those who have not displayed any symptoms. When someone has been infected, their body will start to fight the infection. One of the main ways the body does this is by developing antibodies that can bind to the virus and neutralise it. In this stage it is possible to test for the circulating antibodies and potentially determine how well a patient is fighting off the virus. Antibody testing is not primarily optimised to diagnose patients in the early, acute stage of the disease; antibodies increase as they mature in later stages of infection.

These antibody tests can support priority screening of high risk groups, such as healthcare workers, delivery service providers, or food supply workers who might already have developed a certain level of immunity and can continue serving and/or return to work. As healthcare specialists understand more about immunity to SARS-CoV-2, the tests could also help society return faster to normality.

However, for tests to provide information of value, they must have high degrees of both specificity and sensitivity. Test sensitivity indicates the ability of the test to correctly identify patients that have the disease (“true positives”). Test specificity indicates the ability of the test to correctly identify patients that do not have the disease (“true negatives”). If a test had 100% sensitivity and 100% specificity it would mean there would be zero false negatives and zero false positives, respectively. Essentially no test today has both 100% specificity and sensitivity, and it is generally a trade-off between these two values. A test’s specificity and sensitivity serve as good indicators of the reliability of the test results.

Broad access to reliable COVID-19 testing is essential to accurately identify who has been infected and to contain the disease. “All countries must aim to stop transmission and prevent the spread of COVID-19, whether they face no cases, sporadic cases, clusters or community transmission,” said Dr. Tedros Adhanom Ghebreyesus, WHO Director-General.3

As healthcare professionals and regulatory authorities gain more knowledge about the disease, lessons have emerged that can be applied to future disease outbreaks. Infectious diseases don’t respect national boundaries − everyone needs to work together to understand, contain and treat the outbreaks. Information needs to be shared early and freely. And, importantly, accurate and reliable diagnostic tests are essential to determining the extent of the outbreak and to identify those most vulnerable.

“You can’t fight a virus if you don’t know where it is. That means robust surveillance to find, isolate, test and treat every case, to break the chains of transmission,” Dr. Tedros said. If you want to find out more about COVID-19 and get the latest information on the pandemic, please visit the

References

1. Worldometer. Coronavirus cases and deaths. [Internet: Cited 2020 April 29].

2. World Health Organization. Novel Coronavirus (COVID-19) Situation. [Internet; cited 2020 Mar 12]. Available from:

3. World Health Organization. Mission Briefing on COVID-19: WHO Director-General’s Opening Remarks. [Internet; cited 2020 Mar 12]. Available from: