As part of our responsibility to provide the information you need to know when you need it, we’ve been taking your coronavirus questions to the experts.
This is a constantly changing situation and answers are current as of time of publishing.
Please check www.health.gov.au for the latest.
Monash University Professor of Medicine Paul Komesaroff, who directs the Centre for Ethics in Medicine and Society, is answering your questions about bizarre cures and the situation with testing.
Over to him.
How reliable or accurate is the COVID-19 test, e.g. What is the rate of false negative results?
No test is perfect and all produce some ‘false positive’ results (that is, where the test shows positive when the person does not actually have the condition) and some ‘false negative’ results (when the test shows negative but the person really does have the condition).
Related ideas are ‘sensitivity’ (the proportion of true positive cases that are actually picked up by a test) and ‘specificity’ (the proportion of positive test results that are correct).
The test being used for COVID-19 detects viral genetic material in samples taken from the mouth or nose of a patient.
If the virus is present in the sample, the test is extremely sensitive and specific – indeed, it is capable of detecting and identifying exceedingly small quantities of virus.
However, the likelihood that a swab taken from an infected person will actually contain viral material is less clear and, presumably, this will vary from person to person and depend on various factors, such as the severity of the disease.
Also, the expertise of the person collecting the sample may be an issue.
Calculating this likelihood is further complicated by the fact that there is no absolute, independent ‘gold standard’ on which we can rely to decide whether a test result is true or false.
However, if the sample is collected and the test conducted properly, the false positive rate is likely to be very low.
Regarding false negatives, the most we can say at present is that, from wide experience with tests for influenza viruses, these rates are 10 to 15 per cent – that is, the proportion of people who show a negative result on a single test who will actually have an infection.
What level of new infections per day is the ‘sustainable’ number, where the healthcare system can cope while herd immunity builds and COVID-19 becomes just another virus?
The answer to this question depends on the severity of disease and the availability of medical facilities to respond to more serious cases.
The level of new infections depends on the extent of testing, detection rates in the community, and the effectiveness of public health measures.
The load on medical facilities also depends on the characteristics of the people who contract the illness, including whether they are older, have pre-existing diseases etc.
The number of people who need to have recovered from an infection to ensure herd immunity depends on the degree of immunity that results from an infection and the kind of contact that people in the community have with each other.
There is no fixed or universal value, but in the coronavirus case it could be 50 per cent or more.
A modelling study has estimated that the number of ICU beds needed is about 10 per cent of the total active cases.
Australia has around 2200 ICU beds at the present time.
These are very rough estimates, but they suggest that if hygiene, physical distancing, and the wider lockdown fail to reduce the rate of increase of new infections, and the ICU capacity cannot be rapidly increased, the latter may be tending towards a maximum when we reach an active infection number of around 20,000.
The virus is able to survive in the air for three hours. Does this mean that if you go into a room in which an infected person was in three hours prior, you can catch it?
Some viruses, such as measles, become airborne and can cause infection to someone entering a room after they have left.
It has, however, not been shown that the SARS-CoV-2 virus can be spread in this manner and it is presently thought unlikely that this will be the case.
A study has shown that when the virus is artificially turned into an aerosol in a laboratory it remains viable for up to three hours.
But this does not mean that airborne particles can spread the infection because to do so, much larger doses than are possible through this route would probably be needed.
Like so many other aspects of COVID-19 this is a question that is likely to be answered as our knowledge expands.
There is a video out that says the COVID-19 virus is destroyed in the sinus nasal passages by raising the temperature in those areas to 56 degrees Celsius. Apparently the virus can survive in that temperature. Is this true? If so, is the recommendation of using a hairdryer and blowing hot air into the nasal passage possibly an effective treatment?
There is no evidence that such a practice could be effective against COVID-19 and it is likely to be dangerous.
It is strongly recommended that the practice referred to be avoided.
There have been many other sham ‘treatments’ that have been promoted through social media, often by unscrupulous individuals seeking to make money from the fear understandably being experienced across the community.
It is important that people know that, as well as being illegal, promotion of false treatments can be dangerous and we must make sure that this is widely understood.
If you have contracted the coronavirus, at what point after are you non-infectious?
People infected with the SARS-CoV-2 virus can infect others, even if they do not have symptoms themselves – in fact, this may be how the disease is most commonly spread.
In people who develop the disease – COVID-19 – viral shedding is known to occur from about two days before symptoms develop and to reach a peak soon after.
The question of how long someone remains infectious is more complicated and may vary from person to person.
The current Australian national guidelines state that:
- If someone has proven disease but has not been hospitalised they should be considered infectious for 10 days after the onset of infection and three days after the resolution of fever
- In positive patients in hospital and health care workers, the above criteria apply, plus the requirement that two tests performed at least 24 hours apart show a negative result
- In patients in the community who have some symptoms but have not undergone testing and have not been overseas or in contact with someone known to have tested positive, it is sufficient to wait 24 hours until after symptoms have resolved
- Community patients who have been overseas or have had contact with people with known disease should wait for 10 days after the onset of infection and three days after the resolution of fever.
It is important to emphasise that this is an evolving area.
Some studies have shown that people recovering from infections may test positive for up to six weeks after recovery, although others have suggested these tests may not correlate with actual infectiousness.
It is likely that these questions will be resolved as further data is collected and more advanced tests become available.