COVID-19: Your questions. Expert answers.
By:London School of Hygiene & Tropical Medicine https://lshtm.ac.uk/themes/custom/lshtm/images/lshtm-logo-black.png
Thursday 2 April 2020
What is the current situation? (26 March 2020)
We are now three months into the current outbreak, which started in December 2019 in Wuhan, China and has since spread rapidly across the world.
The number of cases in the countries first affected by the virus have fallen due to the strong measures taken. In China, no new cases have been reported for a number of days. The outbreak is currently affecting Western Europe and increasingly the USA worst. Measures taken so far to control the outbreak include quarantine, case detection, self-isolation, treatment, contact identification and contact isolation, and the introduction of physical distancing measures in general society to stop further transmission. Such measures have worked in Asia and are now being tried in many of the affected countries.
One of the challenges we face in our current strategy is the limited testing capacity, and with access to testing being highly restricted so we don’t really know where and how many cases there are. This is why physical distancing in populations in so important, as it is one of the few measures we have to slow the spread of the virus.
How do tests for COVID-19 work?
Currently, COVID-19 tests are done using nose swabs, these look for virus particles within the upper respiratory tract. The test identifies whether there is an active infection now, though it doesn’t tell you whether you have been infected in the past.
How reliable are the tests? Do we have anti-body tests that work?
The standard PCR (see below) tests for diagnosing COVID-19 are highly accurate if performed technically correctly. The tests identify fragments of RNA from the virus itself. In terms of an anti-body test which shows if you were infected in the past, we don’t yet have data on how accurate these are. Several different tests have been developed and we will have to wait for evidence to learn more about their accuracy.
[Polymerase chain reaction (PCR) is a method widely used in molecular biology to rapidly make millions to billions of copies of a specific DNA sample allowing scientists to take a very small sample of DNA and amplify it to a large enough amount to study in detail.]
Can you be re-infected with COVID-19? Or are we immune to it if we have had it once?
There have been a few isolated reports of people testing positive, then negative, then positive once again. This could likely be due to a sampling or technical issue, rather than a repeat infection. The great majority of people only get infected once.
Based on what we currently know, it looks like a person becomes immune after contracting the virus once. What we don’t know yet is for how long - it could be for one year, for 10 years or even for an entire lifetime.
What about herd immunity?
[Herd immunity is resistance to the spread of contagious diseases within a population, which happens if a high enough proportion of individuals are immune to the disease, limiting its spread, especially through vaccination].
We refer to herd immunity when talking about vaccines. Vaccines are a good way to expose people to an inactivated virus to create antibodies, virus without getting infected by the virus. For a new virus, such as the novel coronavirus it is a different story, it is a riskier issue to count on a virus to create herd immunity, as it will make a lot of people sick and even lead to deaths first.
How can co-morbidities influence the course of infection with COVID-19?
The main co-morbidities identified as particularly dangerous for people infected with COVID-19 are cardiovascular diseases, diabetes, obesity, and the like. People suffering from these conditions already have existing health problems and their immune systems are not as robust. Their capacity to take on additional illnesses is therefore reduced and their bodies can get overwhelmed, for example when they get pneumonia because of COVID-19. That is the main reason for higher death rates among people with such co-morbidities.
Why are we seeing such a big number of COVID-19 cases in Europe but not yet in Africa?
Part of this is due to human travel and trade movements. There are strong links between African countries and China for trade, but these are even stronger between China and Europe, so it is not surprising the virus reached Europe first.
We are starting to see cases in a large number of African countries and these may become hotspots in the coming weeks and months. Many countries have testing in place, however weak health systems could become a problem. One potential upside could be that the African population is quite young compared to China and Europe, and we know that younger people tend to be relatively well spared from effects of the virus. On the other hand, we don’t know yet what impact the virus will have on populations with high levels of HIV, tuberculosis, and malaria.
How can we ensure that vaccines or treatments reach vulnerable people in the global south?
We don’t have a vaccine yet, but we are getting ready for when one does become available. Discussions are underway on distribution, and how to ensure equitable, global access, especially in priority areas and for vulnerable population. This includes the elderly and health care workers. In the meantime, we have to use what is already available – things like case detection, physical distancing, and restriction of movements to prevent virus transmission.
What is the risk of a second wave of the virus?
There is a risk of a second wave. When we look historically, for example, at the 1918 pandemic, it had a very serious second wave.
In Hubei, China, due to successful control measures they have had no new cases recently. Authorities and population there are now keen to relax restrictions - but only a small proportion has actually been infected, so the rest of the population are therefore vulnerable to reinfection. If the virus was to get in through reduced travel restrictions, we could get a second wave there. In Hong Kong, we have seen a recent surge of cases, due to citizens returning to the country after term time, who have brought the infection back.
So our concern now is to get through this first wave, and then see if we can start loosening our guard, but we will have to watch this very carefully.
Do we know why children seem to be less affected by COVID-19?
There seem to be two factors involved here. On the one hand, children seem to get exposed less and get less sick if they do get infected. This has to do with social mixing, which doesn’t happen randomly. On the other hand, we know there is a consistent age gradient with COVID-19. So the younger you are, the better you are able to fight it off. We still have an incomplete picture however, because it’s a new virus.
What is the science behind using anti-malarial drugs for the treatment of COVID19?
Anti-malarial drugs are one of the frontrunners of drugs that are being repurposed. There are trials going on, but we don’t yet have definitive evidence whether they work or not.
There are two possibilities how such drugs could be used: One is as prophylaxis - taking it to stop you from becoming infected. But this would require large supplies of the drug for a long time. A second option is to use the drugs for treatment when a person is already infected - but it probably would have to be given early on to work.
However, there are still a lot of uncertainties around repurposing drugs and high risks of rumours circulating. We don’t yet have evidence of the effectiveness of these drugs for COVID19 and it is therefore very important not to attempt home remedies. There have been cases where people have tried to self-medicate and have become quite ill from that self-medication.
We know that physical distancing works, and we urge the public to stick with what we know and look forward to scientific results moving forward.
Do we know if transmission is airborne and can it linger on dust?
It looks like the main modes of transmission are through droplet spread and via contaminated surfaces. People touch contaminated surfaces, then their eyes or mouth, and become infected. There is evidence suggesting the virus can survive on some surfaces for several days, which is why cleaning surfaces and washing hands is extremely important to stop yourself from getting infected.
Studies also show that there can be aerosol spread. This means virus particles float in the air and are infectious if you inhale them. This is a big concern for health care workers who are in close contact with patients. For the general public that is less of an issue - physical distancing and handwashing will be equally effective against all forms of transmission.
Why do guidelines around PPE (personal protective equipment) change so often?
We are learning new things every day, so in terms of PPE guidelines changing, this doesn’t mean that previous ones were wrong - just that our knowledge has evolved. Guidelines are being adapted to new learning, opportunities and products that become available.
Why are there such mixed messages on the effectiveness of using face masks?
We only have very limited evidence to show that face masks protect you from getting infected. Many of the masks used don’t give you protection, and are also often not used properly.
They are of use for people who are infected and coughing and sneezing, however these people should be self-isolating, so it shouldn’t be a practical situation that exists. In the early wave of the virus we saw a problem with people hoarding masks, meaning that people who needed them were not be able to access them. It’s important to remember that this outbreak is not about individuals; it is about everyone cooperating. So take the precautions you need on an individual level, but be aware that others may need protection more than you do.
How are the World Health Organization (WHO) and other institutions engaging with scientific communities to make sure new scientific advances are communicated rapidly?
The WHO has a number of mechanisms in place to facilitate collaboration with companies and also research institutions. Everyone sees sharing of knowledge as an important concern whilst keeping everyone posted on what is in the pipeline. The WHO has been proactive at multiple levels to ensure this, but it needs the cooperation of research institutions, governments and companies.
What role has blame and stigma played during the outbreak?
Blaming has happened at multiple levels, including at the level of leaders, where blame has been assigned to other leaders for certain issues, particularly perceived inaction. This hasn’t been productive. At a community level, stigma and blame are also an issue. Initially, when COVID was a phenomenon directly attributed to China, there was a lot of discrimination and even harassment of people from China or even Asia. This has changed now somewhat as COVID has become a global issue and anyone might be infected. Again, this is a time for cooperation and respect as we are all in this together.
Could warmer weather slow the spread of the infection?
As this is an unfamiliar virus, we don’t yet know very much its transmission varies in different climates. Other respiratory viruses do tend to have seasonality patterns and are worse in colder winter months. In the tropics, they circulate all year around. If we take a look at Australia however, it does seem like the virus is spreading despite the warmer temperatures.
Heidi: It is important to keep up with information, but also don’t believe everything you read without cross checking with trusted information sources. There are a lot of things circulating that are not true. My advice would be to read with caution and look for reliable sources such as the WHO, US Centers for Disease Control and Prevention (CDC) and national health institutes, which base their information on scientific evidence.
Jimmy: We are all in this together, we need to cooperate, listen and follow advice that we are being given about physical distancing to protect ourselves, our families, loved ones, neighbours and friends. We need to follow those messages. This epidemic will get worse before it gets better. The more we comply the sooner we get ahead of this pandemic and get towards a situation where we can relax these strict controls.
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