As we continue to navigate these unprecedented times, KCBS Radio is getting the answers to your questions about the coronavirus pandemic. Every morning at 9:20 a.m. Monday-Friday we're doing an "Ask An Expert" segment with a focus on a different aspect of this situation each day.
Today we're looking at the coronavirus itself - what we now know and what we still don't - with Dr. Angela Rasmussen, Colubmia University Virologist.
Q: Is there some antibody activity generated, not just by this virus, but other related viruses as well?
A lot of studies have been done so far during this pandemic to look at whether there may be cross-reactive antibodies to the other coronaviruses that normally circulate during cold and flu season. There are four other coronaviruses that typically cause flus and colds, and we've probably all been exposed to some of them. The problem with this is that there probably isn't a lot of cross-reactive antibodies because these coronaviruses are actually fairly different from SARS-Coronavirus 2. Two of them are in the same larger group, called Beta Coronaviruses, but they're sufficiently different that we probably don't generate very many antibodies that might react with SARS-Coronavirus 2. However, the good news is people have also been looking at T cell responses, which is another aspect of the immune response that doesn't get as much attention as antibodies. It does appear that there may be some cross-reactive T cell immunity to those other coronaviruses that can also provide some protection against SARS-Coronavirus 2, but this is still a very active area of research.
Q: This notion of adaptive immunity - do we have a sense of what immunity we might have if we’re exposed to the coronavirus?
We are definitely getting a better sense of what immunity to this coronavirus looks like. We do know that most people who are infected with this coronavirus will develop some level of antibodies. In fact, most of those antibodies are what we call neutralizing, meaning that those antibodies which are floating around in your blood can bind to the virus and render it non-infectious. This is very important for protecting you against future infections. Another study out of South Korea showed that people who recovered from Covid and tested positive again actually didn’t have any infectious virus circulating in them, meaning that the positive test was probably just detecting some residual dead virus genetic material that was still in their systems. So that’s an encouraging sign too that indirectly suggests that people are not going to be re-infected, at least in the short term, after they’ve recovered from Covid and developed against antibodies against the virus. What we don’t know is how long this immunity will last, and we don’t know how protective it is. Will it protect you unconditionally or are you still susceptible to maybe getting infected but less disease? Those are questions that are still being looked into.
Q: On the notion of asymptomatic infection, are we seeing many more people with antibodies than anticipated?
One thing that has been very confusing has been discussions of asymptomatic versus pre-symptomatic people. It’s very difficult to determine people who are truly asymptomatic for the entire course of the infection. Meaning they are infected, they have virus, they might be shedding virus, but they never get any kind of detectable symptoms or any kind of detectable sickness. That’s very difficult to determine because oftentimes that relies on people reporting their own symptoms. Even people like me, who think about this stuff a lot, don’t always recognize that maybe that scratchy throat is actually a symptom. What we do know is that a lot of people can transmit the virus when they are pre-symptomatic, meaning they don’t know that they are infected, they don’t know that they are sick, and they don’t feel sick yet. They will go on to get sick, but during that period where they don’t know they can transmit it to others, and that has been a particularly challenging aspect in terms of stopping the spread of this virus.
Q: In the March/April timeframe we heard reports about companies developing an antibody treatment that might provide a stopgap until there’s a vaccine. I haven’t heard anything about this recently, have we heard something about this that makes it not viable?
I don’t think so, I think the problem with that is that antibody drugs are typically very expensive drugs to use. It would be very difficult to scale up a product like that and use it over a wide population in terms of a prophylaxis. Certainly what would be better is if there was a drug that could reduce your risk that is already available, that is already being manufactured, that could be distributed. I think that issues with manufacturing and probably testing, since you need to be able to make sure drugs like this antibody work, that’s very difficult to do and requires a lot of subjects in a randomized control trial. I suspect the reason we haven’t heard much is that work is still ongoing and it takes a long time to do it.
Q: Are you concerned that Covid-19 might have an acute impact on the severity of the flu this year and what is the possibility of contracting both?
I think that’s a huge concern, certainly we don’t know what kind of flu season we’re in for yet. Some years we have a milder flu season than others. Certinalty the increased strain placed on hospitals by the Covid pandemic could make things worse for people who have influenza or severe influenza, which already does strain our hospital resources in particularly bad flu seasons. So we don’t really know what that’s going to look like. And we also do know much about co-infection, a patient who has severe influenza and Covid-19, but they are all concerning prospects from a public health perspective. I would retirite the importance of getting a flu shot, because you definitely want to reduce your risk for influenza as much as you possibly can.
Q: If the incubation period is 14 days, why did our 10-12 weeks of distancing and closures not had a more dramatic impact on new cases?
This actually has had an impact on new cases, we’ve certainly flattened the curve. We have certainly reduced transmission, but I think one message that often gets lost in discussing this is the fact that flattening the curve doesn’t mean eradicating the curve. We haven’t completely stopped Covid transmission, so even though it may be 6 different life cycles of coronavirus, there is still transmission occurring in the community. It’s that low level of cases that is going to continue the spread of this coronavirus. The only way to safely reopen without lockdown is to make sure that the amount of spread is so low that we can actively break chains of transmission by doing good old fashioned epidemiology. Testing widely to find cases before they even know that they’re infected and have a chance to transmit the virus, isolating infected people, tracing their contacts, quarantining their contacts, and testing them. That is how we will be able to break the cycle of transmission, so far all we’ve been able to do is reduce it.
Q: What does the reproductive number mean for the virus, and why is 1 so important?
This is one thing that’s been very confusing. That number is really an average, it doesn’t mean that every single person is transmitting it to one person. It means that, on average of all the people who have gotten it, there was transmission to one person. Actually the real magic number is less than one, so you want the majority of people to be transmitting the virus to less than one person, which is zero. When you reduce it below that level, the transmission in a community is sufficiently that you can contain the virus using the epidemiological measures I mentioned above. When it’s higher it means that there is so much transmission occurring that there is no way to effectively identify all the cases and conduct contact tracing to break those chains of transmission.
Q: Do we really know who infectious this virus is compared to other viruses or the common cold?
We do know a little about this. This virus does seem to be at least as transmissible as influenza. We don’t really know how transmissible many of the common colds are because you are actually talking about hundreds of different viruses from different families. Also, a lot of the time when you get sick, when was the last time you went to the doctor with a cold and asked them to affirmatively diagnose you with a specific virus. Usually that doesn’t happen, so we actually don’t have hard and fast numbers about common cold transmission, and in some cases about influenza transmission. We do know that this virus is very transmissible, and we know that it’s very transmissible by people who don’t yet know that they’re infected. Those things are probably what are continuing to drive the spread on a pandemic level.
Q: Is that pre-symptomatic transmission much different than these other viral diseases?
No, there are a number of other viruses that can be transmitted when a patient is pre-symptomatic. That includes everything from influenza, ebola, even blood-borne viruses such as Hepatitis C can be transmitted by people who are completely non-symptomatic so they don’t know that they’re infected to transmit it. The problem with this virus is that, unlike influenza, we don’t have any pre-existing immunity and we don’t have a vaccine for it. Unlike HIV or Hepatitis C, those viruses are not transmitted by the respiratory route. So the problem with this virus is it’s transmitted by an easily transmissible route, as well as when it’s transmitted when they don’t know that they’re actually sick.
Q: Studies show that people with higher amounts have Vitamin D in their blood have a lower case load than those whose blood is low in Vitamin D. Why isn’t this being more widely available?
This information is pretty widely available, but this is a great example of the old scientific adage that correlation does not equal causation. There are many other explanations and variables that go into Vitamin D deficiency, and it’s certainly worth further study. It’s worth looking into this link as something that might be possibly used to treat Covid potentially even, or prevent Covid. But right now it’s nothing more than a correlation that deserves further investigation.
Q: Could the virus spread on the packaging from meat and poultry plants that have so many infected workers?
That’s very unlikely. We do know that the virus can remain infectious on plastic surfaces for some period of time. That’s dependent on a lot of other variables such as temperature and humidity levels, as well as how that package is being handled. The important thing to remember is that most surfaces, unless they are high-touch surfaces like a door knob or a communal counter top, are not going to have a lot of virus all over those surfaces. They may have virus in one or two places where someone has touched them or potentially sneezed on them, and that amount of virus really matters a lot in terms of whether it can infect you. One thing we don’t know about this virus is how much virus you actually need to be exposed to in order to become infected. With the time from taking the meat from the plant to the grocery store, that will reduce the amount of infectious virus that’s on the package. If it’s only on a small part of the package, you may not have enough on the package in the grocery store for you to become infected. That said, it’s very important to keep washing your hands and practice good hand hygiene whenever you’re out in public, or handling other packages or materials.
Q: I heard the virus can live two years in the freezer, has this been proven or disproven?
It hasn’t been proven for this virus, we haven’t had two years with this virus so we don’t know explicitly how long it lasts in the freezer. That really does depend on a lot of different factors. Most people have frost-free freezers, they cycle between different temperatures to prevent the build up of frost. That cycle is really harmful for viruses, we can’t use frost-free freezers in the lab for that exact reason. So I think in a home freezer, virus persisting for even a couple of months seems remote, but we can’t rule it out because we haven’t tested it.
