The 'R' Factor

The lockdowns are working. The coronavirus is retreating. One of the most basic metrics in epidemiology, the legendary R, has fallen below 1 in New York, which means that, on average, each infected person is spreading the infection to fewer than one other person. So long as that stays true, the epidemic will recede.

After a weekend when hundreds of New Yorkers died, this may sound like a view through heavily rose-colored glasses. In fact, this rate of transmission, or reproduction, is vital to what we can do next and when we can do it.

In other countries R has become a part of the public conversation. In Hong Kong, the School of Public Health issues a regular update (R was .2516 last Friday). Chancellor Angela Merkel gave the German public a tutorial on R that reminded everyone of her doctoral training in quantum chemistry.

But in the United States we have tended to focus on other data until just the last few days.

On Friday, Dr. Tom Frieden, who has held two of the most important public health jobs in the country, director of the Centers for Disease Control as well as Health Commissioner of New York City, said by Zoom from his home in Brooklyn that the transmission rate has been driven below 1 here. The next day Governor Cuomo reported that the rate is now .9. Encouraging, although, as he noted, not nearly as good as the .3 Wuhan reported as it curbed the virus there.

State and city officials have shared a great deal of data to help New Yorkers appreciate their plight and accept the restraints. Some of the data comes with goals to achieve before restrictions can be loosened. The City Health Department, for example, set as one of its three milestones a rate of daily hospitalizations for COVID-19 symptoms below 200. On April 8 there were 631 new coronavirus patients admitted. Saturday the number was 212.

Tracking R in Real Time

Hospitalizations, crucial as they are to managing the medical system, aren’t a metric individuals readily identify with. Which is why understanding R, as esoteric as it may at first seem, is vital. For the next year or two, R will be our north star as we try to resume some semblance of regular (let’s not even say normal) life and work. Frieden and his colleagues wrote an article last week describing the value of tracking R in real time because of its “important implications for disease control.”

First a crash course. R, sometimes called Ro or Rt, is the number of people an infected person would be expected to give the infection to. Aboard the Diamond Princess, R was 14, Frieden said, and possibly as high as 5 in the early days of the epidemic here in New York.

Three factors combine to create this number, Frieden’s team at Prevent Epidemics explains: How long a carrier is contagious, the number of people that infected person comes in contact with and how easy the virus is to pass along the virus.

The lockdowns have focused on radically reducing contact and making it harder for the virus to pass from an infected person to others. These efforts appear to be shutting down the virus. But they also have shut down the economy.

Boxing in the Virus

Can we find a new approach that lets economic life resume while controlling coronavirus? Frieden says yes, but we have to change the conversation. “It’s not about when we can reopen,” he explains, “but what we have to do to make that date come sooner.” It is about what needs to be in place to restart safely, Frieden says in a matter of fact way that doesn’t directly criticize the public officials who have tried to set the date first.

Frieden gave a briefing Friday to describe how to box in the virus (#BoxItIn). There are four components and if any are weak the virus can escape.

The first has received a lot of attention. That is testing. We are still weeks away from being able to conduct enough tests. Tests are also just a first step, Frieden said. Second, everyone who tests positive must be isolated. That is, instead of isolating everyone from everyone, as under the present lockdowns, we need to isolate those who are contagious from the rest of us. That can be at home or in hotels or other facilities set up to house them. “It’s pretty easy to book a room in New York City right now,” said Mark Levine, chair of the New York City Council’s health committee.

Third is to trace everyone the infected person came in contact with and, fourth, isolate them too, if they may be contagious. This, as Frieden pointed out, will require “an army” of sleuths who can win the trust of covid-19 patients and coax them to share the names of who they’ve had contact with.

The health department is looking at city workers who might be reassigned to this task. But there is also no shortage of out-of-work New Yorkers who could be trained relatively quickly.

In Massachusetts, which was hit early and hard by the virus, the state has brought in a global NGO with extensive experience tracking down and snuffing out infectious diseases in Africa and Haiti. “These are things we used to know how to do in the United States,” said Dr. K.J. Seung, chief of strategy and policy of the Massachusetts COVID response for that not-for profit, Partners in Health.

But it has been a long time since infectious disease was a main health challenge and our medical system is built now for non-infectious diseases. “We cannot ICU our way out of this crisis,” said Seung. “There’s no vaccine. There is no real treatment. You have to go back to public health 101 - Testing, isolation, quarantine.” Or, #BoxItIn.