By Dr. Radha Rangarajan
Coronavirus outbreak: The COVID-19 epidemic is now sweeping across the globe with over 187,000 people in 117 countries affected. The statistics are dumbfounding. In a matter of weeks, we have moved from containment as a goal to slowing the epidemic. What's fueling such a rapid spread of the disease? Let's first understand that COVID-19 is a zoonotic disease, which most likely spread from bats to humans via an intermediate host.
COVID-19 symptoms: Touching surfaces infects next individual
For the majority of those who fall sick, the symptoms are minor. When infected individuals cough and droplets of saliva and mucus are expelled, the virus gets onto surfaces in the environment. Touching such surfaces and then the face allows the virus to infect the next individual. The basic reproduction rate, R0, of COVID-19 is 2-3, meaning that each infected person can infect 2-3 people.
Despite a low R0, the number of cases globally has been high. This apparent paradox is a result of two key factors. One, the virus has a long incubation period, almost 14 days, during which people do not show symptoms. Second, people who recover shed viruses as long as 20 days after symptoms have subsided. During these periods, they have the potential to infect a number of individuals unknowingly. Extending the isolation period during the recovery phase can halt post-recovery transmission but that alone is not enough. Identifying those who are infected and asymptomatic or have mild symptoms and isolating them early is the most effective way of slowing transmission.
COVID-19: What do we know about India's current capacity for testing?
Tests for COVID-19 involve giving a nasal swab to an authorized laboratory, where the genetic material is extracted and COVID-19 specific genes are amplified. The Health Minister has said that India currently has approximately 100,000 tests available. Considering that each patient is tested twice and immediate contacts of those who are positive must also be tested, a logical question is: are we sufficiently well-stocked?
Consider South Korea with its population of around 51 million people. The country is reporting a gradual decline in the number of new cases since the end of last month, despite having had a high burden of 8000 infections. It has tested 250,000 people since January, approximately 3600 people per million. If we apply this metric to India, we need about 36 times what we currently have! Even if we take a more conservative view, it is clear that the production or import of kits has to be significantly ramped up.
Currently, only 63 laboratories are authorised for testing. If we want to improve access and enable widespread screening, the test will need to be offered by hundreds of laboratories, across the country. Such a decentralized model has been adopted by Germany and has likely contributed to their low fatality rate. Germany has had over 6400 cases and only 16 deaths, approximately 2.5 per 1000. The highly distributed and large network of laboratories in Germany, ensured that people with even minor symptoms were tested locally and rapidly. Others such as South Korea, went one step further, moving the test out of the laboratory. Using drive-in facilities to randomly test people, they were able to identify positive individuals proactively. Ultimately, these efforts led to the early isolation of people.
Coronavirus outbreak: Increasing lab capacity, volume of kits
While the strategy of increasing laboratory capacity and volume of test kits is necessary, it is also time to consider the type of technology that is employed for testing. A test that is accurate but complex and takes time to complete does not scale well. Hence, alternative technologies must be considered.
Rapid diagnostic tests (RDTs), akin to pregnancy tests, that give results in minutes and can be performed at home are one such example. Making sure that the test is paired with a mandatory tele-consultation platform through a mobile phone would allow the results to be monitored.
Although RDTs tend to have lower sensitivity and specificity than a laboratory test, they serve the purpose of a screening test, segregating those who do not have the infection.
More than four manufacturers across the globe are now starting to deploy such tests, focusing on Europe. India can quickly validate these tests and expedite Regulatory approvals. It will allow the country to greatly expand its testing capabilities in this hour of need. In fact, a strategy of using RDTs followed by confirmatory laboratory tests will be of great use in Africa as well. By taking the lead now, India can establish the appropriate protocols and testing hierarchies for the global community.
In sum, we need to move towards a strategy of testing widely and isolating early. This will enable India to ride out the COVID-19 storm without high fatalities.
The columnist is Chief Scientific Officer, HealthCube. Views expressed are the author's own.