Here are some of the latest developments in covid-19 research, including whether people can develop immunity, the effects of covid-19 on the brain, and the potential for the pandemic to grow even larger than it has already.
Covid-19 and psychosis
The full range of health effects of the coronavirus, which has infected at least 4.5 million people and killed over 300,000 worldwide, will take years to figure out. But in a new paper this month, researchers in Australia and the UK concluded that a small slice of people will likely suffer drastic mental health problems as a result of the pandemic, up to and including psychosis.
The paper, published in Schizophrenia Research, is a review of the medical literature surrounding psychosis and pandemics. The researchers describe reports of acute psychosis documented during past flu pandemics. They also cited research linking an increased risk of schizophrenia among children whose mothers contracted the flu while pregnant during the 1918-1919 pandemic.
Some of the treatments used to save people seriously ill with covid-19, such as steroids, have also been linked to a slightly higher chance of later psychosis.
But it isn’t just the coronavirus itself that could be a risk factor for psychosis; the stress of the pandemic, isolation, and economic devastation may also contribute to mental breakdowns.
These effects won’t be universal, and in fact, in some places, the pandemic might even engender a greater sense of community as people band together to fight a common enemy. An added risk of psychosis from covid-19 will likely be very small for any one person and only noticeable when looking at the population level. But for some of us, it’s possible that covid-19 won’t just affect the body, but the mind as well, the authors warn.
“The main finding from our rapid review is that there is moderate (if low quality) evidence to suggest a small but important number of patients will develop coronavirus-related psychosis that is likely associated with steroid or viral exposure, pre-existing vulnerability, and psychosocial stress,” they wrote.
The size of France and Spain’s pandemic
One of the most important questions about covid-19 is how prevalent it is, i.e., how many people it has infected so far. It’s very likely that surviving an infection will provide a buffer of immunity against the virus in the future, at least for a while. If the percentage of people who have had covid-19 is high already, then it makes sense to start easing up on restrictive measures intended to slow its spread. Unfortunately, research this week is the latest to suggest that we’re not even close to seeing the worst of covid-19.
In a study published Wednesday in Science, researchers tried to estimate the infection burden of France, one of the countries hardest hit by the pandemic. To create their model, they relied on data from the outbreak onboard the Diamond Princess cruise ship, which saw over 700 cases and 14 deaths. Because the Diamond Princess outbreak was isolated and meticulously tracked from beginning to end, it likely provides a sense of how infectious, life-threatening, and fatal the virus can generally be in a population.
Mapping that data onto France’s reported outbreak, including hospitalizations and deaths, the researchers estimated that about 4.4 per cent of the country had contracted the virus by May 7. They also estimated the overall fatality rate to be around 0.7 per cent but as high as 10 per cent for people over 80.
The numbers aren’t too surprising, since they line up with other research, including studies in France that used blood tests to look for people’s antibodies to the virus, indicative of having survived an earlier infection. On Wednesday, the government of Spain released its own preliminary data from an ongoing antibody study, currently involving 60,000 residents. It estimated that only 5 per cent of the country has caught covid-19. In in the capital city of Madrid, an estimated 11 per cent of people have have already had it.
These findings, if accurate, don’t bode well for the world at large.
As of May 15, France and Spain have reported the fourth and fifth most deaths, respectively, both with counts over 27,000. So it’s likely that no country has had much more exposure to the virus, meaning that the pandemic can still grow far larger, especially if areas start to lift lockdowns without plans in place to prevent new waves of infection. In other words, herd immunity won’t save us anytime soon, and it’s likely many more people would die if such a strategy is pursued.
“Population immunity appears insufficient to avoid a second wave if all control measures are released at the end of the lockdown,” the authors wrote.
T-cell immunity to the coronavirus
Here’s some encouraging news to close things out.
Much has been made of the importance of having antibodies to the coronavirus, which may protect a person from reinfection. But immunity is more complicated than that. Antibodies are just one of the weapons our bodies use to fend off germs we’ve encountered before. Another is certain types of T-cells, called CD8+ and CD4+ cells. These cells, like antibodies, are created and keyed specifically to target a virus that shows up again. Some viruses, however, have found ways to evade this immune response, and it wasn’t clear whether the same could happen with the coronavirus.
A new study, published in Cell this week, suggests that it’s probably not going to be a major worry with covid-19. Researchers studied blood samples taken from 20 recovered, non-hospitalized patients who had been symptom-free for at least 20 days. All of the patients appeared to carry specific CD4+ cells tuned to the coronavirus, while 70 per cent carried specific CD8+ cells; they also had antibodies to the virus.
CD4+ cells, or helper T-cells, are crucial to immunity because they activate or help other immune cells, including those responsible for pumping out antibodies, while CD8+ cells actively seek and kill their targeted germs. Some amount of both types of cells in the study also responded to the spike protein found in the coronavirus. That’s important, because many potential covid-19 vaccines hope to mimic the spike protein, so it suggests these vaccines will be capable of creating a strong immune response.
Taken with other research, it’s an early but good sign that most people can develop immunity with ease. It’s still unclear whether this immunity will be long-lasting or if there are significant exceptions to the rule, but it’s positive news nonetheless.
The researchers also found evidence that our encounters with other, less dangerous coronaviruses—those that simply cause the common cold—may have better prepared some people against covid-19. In about 40 to 60 per cent of unexposed people (people who donated blood between 2015 to 2018), they found CD4+ cells that reacted to the new coronavirus. More research will be needed to prove whether having these older cells actually provides some protection, but it’s a possible factor that could have a “very substantial impact on the overall course of the pandemic, and the dynamics of the epidemiology for years to come,” the researchers wrote.