South Africa faces a significant shortage of Covid-19 test kits if testing for the novel coronavirus needs to be ramped up, scientists and virologists warn.Test kits are imported and experts say that both the public and private sector are already under strain to provide enough kits for the demand for tests at the moment. Most of these tests are also only conducted when symptoms become prevalent.Three scientists directly involved in testing for and research about the spread and containment of the Covid-19 virus say there are serious concerns whether the country's health system will be able to manage the amount of testing when random tests and tests on demand increase. Dr Marvin Hsiao, virologist and principal pathologist at the National Health Laboratory Service (NHLS) at Groote Schuur Hospital in Cape Town, said laboratories are already functioning at the limits of their capacity.Inundated Dr Allison Glass, a clinical virologist at Lancet Laboratories, said both public and private laboratories are "inundated" with tests for the coronavirus.Professor Diana Hardie, head of the diagnostic virology laboratory at the University of Cape Town, said although government has now acted, South Africa might soon be "in a bad way".At least 85 people have tested positive for the virus, as of Tuesday evening. President Cyril Ramaphosa on Sunday night announced a number of measures to contain the spread of the virus, including travel bans and the prohibition of gatherings of more than 100 people.As fears mount about the increase in confirmed cases, there have been calls for the country to start testing for the virus more proactively and regularly. On Tuesday, the World Health Organisation's director general, Dr Tedros Adhanom Ghebreyesus, called for countries to "test, test, test". He said more tests were being produced every day to meet demand.But experts interviewed by News24 this week winced at the idea, and said this is simply not possible at the moment.Covid-19 test kits, including elements such as reagents (substances used in chemical analysis) as well as related equipment like swabs and masks to protect healthcare workers, are all imported from overseas. These mostly come from places badly affected by the virus, including Europe and South Korea.For now, the laboratories are testing only symptomatic patients. But if they need to start testing more widely, especially in the event of community transmissions, there may not be enough kits to go around.Scant resources This has led to calls from virologists that asymptomatic people not flood labs with requests for testing, as is currently the case.People without clear symptoms or, in some instances, clear evidence that they were in close contact with a confirmed Covid-19 case, will most likely be turned away. This is to save on scant resources.Hsiao, who also works for the University of Cape Town's virology department, told News24 that all of the test kits that South Africa uses to test for Covid-19 are imported. Labs therefore need to prioritise which cases are tested."At the moment, the majority of the transmissions are still happening from symptomatic people. So it makes sense to focus on people with symptoms. Others might have travel histories (traveled to countries with high infection rates), but at least in our setting we just don't have the capacity to deal with every returning passenger."Glass said resources are equally constrained in the private healthcare sector. She said that South Africa has actually outperformed countries like the US and some European countries in terms of the speed and number of tests. South Africa's scientists have also worked quickly to prepare more laboratories for specialised Covid-19 testing and have tried to diversify their suppliers to ensure a steady supply of equipment.But with the demand for tests being as high as it is and fears that the situation will escalate, Glass is worried."We appeal to the public: if there is no clear reason for testing, such as no symptoms, we discourage asking for tests," said Glass.She said that pressure from people who don't need to be tested slows down the process for those who do. People who request testing without a clear reason, like showing symptoms of the virus, were clogging the system.Testing sites "On the public health side, they are rolling out a number of testing sites in a drive to get everyone up to speed. But the concern is whether suppliers will be able to keep up because we are so reliant on international supply."If countries decide to impose export duties on products produced there, the price of the tests will also increase. Were a country to decide to stop exporting products to preserve the supply for themselves, the impact on South Africa would be nothing short of catastrophic.Hardie says there has been a massive effort to ramp up testing from two weeks ago, when only the National Institute for Communicable Diseases (NICD) had the capacity to do testing. "But there are limitations in acquiring testing equipment. It will take some weeks to expand testing capacity," Hardie says. "We import pretty much everything in the kits and the instruments used as well."She said that both public and private facilities were trying to stock up on supplies in the thousands.Internal transmissionWhile SA is still testing symptomatic patients, this is not yet an issue. But once there is evidence of community transmission of the virus, this will probably change and far more people will need to be tested, she said.While there are still many unknowns, including what impact the virus will have on HIV positive people, it is "reasonable" to expect that SA's situation will worsen, she said.Hardie added that the constraints on resources at labs would have been far more serious without government's drastic interventions on Sunday night. "Had nothing been done, we may not have yet been in a bad way. But a bad way would be coming," she said. The Department of Health did not immediately respond to questions on Tuesday afternoon.