Enlarge / Two classrooms had to be shut down due to a series of problems with maintaining policies meant to limit the spread of the pandemic. (credit: Andrew Lichtenstein / Getty Images )

On Friday, the CDC released a report that traced the spread of the Delta variant through a California elementary school. It's tempting to make this into a story of gross irresponsibility—a teacher was unvaccinated and read to the class while unmasked. But beyond that, it provides a number of warnings about how our public health system remains under stress as we close in on two years since the start of the pandemic. It also reemphasizes how the Delta variant ensures that small errors can easily explode into big problems.

One bad apple

The school in question was a small one, with only a bit over 200 students and 24 staff. It is an elementary school, meaning that its student population is also younger than the cutoff for approved vaccine use. The school did a number of things right, though. Class sizes were kept small, and individual classes were kept in separate rooms, with doors and windows kept open and air filtration equipment installed. There was also a standing policy requiring mask use in place.

But not everything was ideal. The CDC notes that two of the 24 staff members were unvaccinated. While the vaccinated can clearly transmit the Delta variant, they are likely to be less infectious, and in a worst case they'd be infectious for a shorter period of time.

Enlarge / Aerial view showing a tractor digging graves in a new area of the Nossa Senhora Aparecida, where COVID-19 victims are buried, in Manaus, Brazil. (credit: Marcio James / Getty Images )

While attention has been focused on the worrying new variants of SARS-CoV-2, there has been some good news: despite the evolution of a number of strains that appear to spread more readily, total COVID-19 cases have been dropping, both in the United States and globally. While there are a number of nations that are still seeing an increase in infections, a combination of reduced post-holiday spread and increased social interventions appear to be getting the surges seen in January under control.

That said, there are worrying signs that, at least in the US, a number of states are making the same mistakes that ensured that the virus never really went away after the first surge in cases. And the spread of many new variants drives home the need to avoid complacency.

Going down

The general fall in cases came up at a recent press briefing from the World Health Organization. "For the third week in a row, the number of new cases of COVID-19 reported globally fell last week," said WHO Director-General Tedros Adhanom Ghebreyesus. "There are still many countries with increasing numbers of cases, but at the global level, this is encouraging news."

Enlarge / Municipality employees remove the famous blue chairs on the "Promenade des anglais" in Nice, southern France, in order to limit opportunities for people to gather. (credit: VALERY HACHE / Getty Images )

With the dramatic rise in infections in the United States, there's increasing discussion of whether states need to go back to severe social restrictions or even lockdowns, in which only essential workers are allowed to leave their homes. But many people aren't happy about the idea of re-entering lockdowns because lockdowns exact both an economic and an emotional cost.

While we're likely to get lots of hard data on economic costs eventually, some researchers in New Zealand decided to look at the emotional toll. They performed a detailed survey at the height of lockdown and found that, as expected, the restrictions had an impact on people trapped in their houses for weeks. But the impact was more pronounced on the young and those who had experienced psychological distress previously.

Lockdown NZ

The public health officials who advocate for lockdowns in response to soaring infection rates recognize that lockdowns exact an emotional toll on people who have to stay in their homes. The trade-off for this toll is the avoidance of death, severe illness, overloading of healthcare systems, etc. And the lockdowns are meant to be temporary; once infection rates drop sufficiently, then less draconian control measures (like social distancing, limiting gatherings, and mask use) can keep the infection rates low.

Enlarge / A woman in France displays a contact tracing app. (credit: DAMIEN MEYER / Getty Images )

There's a standard set of best practices for disease outbreaks that includes a process called contact tracing. Each time you identify someone infected, you figure out who they've been in proximity to during the time they were infectious. You then get the person infected to self-isolate, and also convince their contacts to do so, at least until they can be tested and found to be uninfected. Doing this successfully can bring the rate of infection down below the point where the outbreak is self-sustaining—even if not everybody's picked up through contact tracing, there won't be many who aren't, and anyone they infect eventually will be.

For the COVID-19 pandemic, infection rates in many countries were initially so high that contact tracing was impractical. But a suite of social interventions—social distance,  mask wearing, limiting time out of the home, washing hands, etc.—were used to bring rates back down to where contact tracing could be effective again.

This didn't happen in the US. There was no national effort to contact trace, each state set its own policy regarding social restrictions, and many states lifted their social interventions too soon , all of which have allowed several surges in infections.

Enlarge / If you can't socially distance, a face mask helps. (credit: Christopher Furlong / Getty Images )

Many countries that controlled their COVID-19 cases in the spring are now seeing rises in infections, raising the prospect that they'll face a second wave of cases, as many epidemiological models had predicted. But in the United States, the number of cases has never dropped to low levels. Instead, it varied between high levels of infection and very high peaks in cases. Why is everything so different in the states?

While there are plenty of possible reasons, a series of new studies essentially blame all the obvious ones: the United States ended social distancing rules too soon, never built up sufficient testing and contact-tracing capabilities, and hasn't adopted habits like mask use that might help substitute for its failures elsewhere. The fact that some of these studies used very different methods to arrive at similar conclusions suggests that those conclusions are likely to hold up as more studies come in.

Too soon

One of the studies, performed by a US-South African team, looked at the relaxation of social distancing rules in the US. Its authors created a list of restrictions for each state and the District of Columbia and tracked the number of COVID-19 deaths in each state for eight weeks prior to the rules being terminated. The number of deaths was used as a proxy for the total number of cases, as the erratic availability of tests made the true infection rate difficult to determine.

Enlarge / Painting by Israel Bernbaum depicting Jewish children in Warsaw Ghetto and in the death camps (1981). (credit: Monclair State University collection)

During the Nazi occupation of Poland during World War II, Jewish residents in Warsaw were forcibly confined to a district known as the Warsaw Ghetto . The crowded, unsanitary conditions and meager food rations predictably led to a deadly outbreak of typhus fever in 1941. But the outbreak mysteriously halted before winter arrived, rather than becoming more virulent with the colder weather. According to a recent paper in the journal Science Advances, it was measures put into place by the ghetto doctors and Jewish council members that curbed the spread of typhus: specifically, social distancing, self-isolation, public lectures, and the establishment of an underground university to train medical students.

Typhus (aka "jail fever" or "gaol fever") has been around for centuries. These days, outbreaks are relatively rare, limited to regions with bad sanitary conditions and densely packed populations—prisons and ghettos, for instance—since the epidemic variety is spread by body lice. (Technically, typhus is a group of related infectious diseases.) But they do occur: there was an outbreak among the Los Angeles homeless population in 2018-2019.

Those who contract typhus experience a sudden fever and accompanying flu-like symptoms, followed five to nine days later by a rash that gradually spreads over the body. If left untreated with antibiotics, the patient begins to show signs of meningoencephalitis (infection of the brain)—sensitivity to light, seizures, and delirium, for instance—before slipping into a coma and, often, dying. There is no vaccine against typhus, even today. It's usually prevented by limiting human exposure to the disease vectors (lice) by improving the conditions in which outbreaks can flourish.

Enlarge / Commuters wear face masks as they travel on the London Underground on June 12, 2020 as lockdown measures are eased during the novel coronavirus COVID-19 pandemic. (credit: TOLGA AKMEN/AFP)

Advice on whether or not to use face masks to limit the spread of the pandemic has varied from country to country, even differing by location within countries. These policies have had to balance whether there were sufficient supplies for medical personnel to divert some to the general public. And the whole issue was decided without a clear idea of whether face masks were actually effective against SARS-CoV-2.

But there has been reason to think masks would at least be somewhat affective, based on studies of the spread of droplets of material we expel while coughing or sneezing. And a recent analysis suggested a large group of individual studies collectively pointed to their effectiveness. But that analysis left a large degree of uncertainty about how effective they'd be at the population level and how face mask use would interact with other policy decisions.

The situation left us needing population-level modeling, which a group of UK scientists has now provided. The group's model indicates that face masks don't have to be especially effective to slow the spread of SARS-CoV-2 and can even bring benefits if they make people more vulnerable to infection. But to really control the pandemic, they will have to be combined with a lockdown if we want to see the total infected population shrink.