UNM researchers: No sign Navajo has reached plateau
In a report to the Health, Education, and Human Services committee two week ago, University of New Mexico researchers said that while measures to reduce the spread of COVID-19 on Navajo have been effective, the Nation has not yet reached its peak, and it would be helpful to have finer scale data to work with.
Johnnye Lewis said that in looking at the COVID-19 data for Navajo, the thing she and her team noticed right off was that much of the early spread of the virus seemed to be linked to the one big church gathering in Chilchinbito.
“That initial front loading of cases really was a major contribution to what we’re seeing, I think,” she said. “It really supercharged the spread quickly.”
Lewis is director of the UNM’s Community Environmental Health Program and co-director of the Navajo Birth Cohort Study at the UNM METALS Center. She has worked with a team of partners on Navajo for over 30 years studying the health impacts of exposure to uranium and other heavy metals.
Lewis said the number of cases on Navajo through April 5 indicated that the rate of growth was substantially higher than in the surrounding states of Utah, New Mexico and Arizona.
By April 21, the data still showed an exponential growth curve, but the slope of the rate of growth had dropped substantially, said Lewis.
This indicated that as measures were taken, including shelter-in-place orders, curfews and shutdown of services, the rate of infections started to decline, affirming that those actions were successful in flattening the curve.
Lewis said the rate of increase in cases has dropped from 12.5% to 8.5% percent.
“That’s the transition from exponential to logistic progression of the disease,” said Lewis.
However, Navajo is still in the steep part the logistic curve and has not yet seen a plateau for cases, she said.
“We’re following the shape of the curve that is going to plateau but we’re not there yet,” said Lewis.
She said because there is still a sustained rate of increase in the numbers they do not have a forecast for a peak for Navajo, which would precede a plateau.
“We have nothing to base that on,” she said.
“We’re not at the point where we can say that this has leveled at all,” said Lewis. “We would really have to see a significant drop — a stable rate of zero to a handful of cases per day for many days running. That’s a plateau.”
Lewis said the Navajo Nation has been doing very well in terms of testing, with 11% of the population tested as of May 11 and 18% of that number of testing positive.
Surrounding states have had a much lower rate of testing, she said, with 3.5% tested with just under 5% of those testing positive.
Lewis said said the mortality rate on Navajo is about 6.5% of confirmed COVID-19 cases, which is almost twice the rate seen in surrounding states, which is about 3.5%.
“We don’t know the reasons for this yet,” she said.
Lewis said it’s possible the higher morbidity rate could be associated with high rates of hypertension and cardiovascular disease, which are major risk factors for complications and severity, or the impact of exposure to metals, which can contribute to immune disfunction, and is widespread on Navajo.
“At this point we don’t know how much of a role that is playing,” she said.
There is also the question of genetic susceptibility to infectious disease, she said.
“Anything that we think we know about this seems to change on a daily basis,” said Lewis.
Until there is some way of protecting people, such as a vaccine or antibodies or herd immunity, there will continue to be spikes especially as measures to reduce the spread of the virus are relaxed, said Lewis.
She said the full impacts of states starting to open up are yet to be seen.
“In another couple weeks, we’re going to have a much better feel for what happens when people start going back out,” she said.
Lewis says testing for antibodies has yet to demonstrate that a COVID-19 antibody response is effective in preventing people from getting the disease in the future.
“Just because a disease produces antibodies, doesn’t mean they will protect people,” she said.
That is true of HIV, for example, where antibodies were present that didn’t neutralize the infection, said Lewis.
“We need a lot more data to see what’s happening,” she said. “Everything about the antibody test is really up in the air right now.”
Finer scale data needed
Lewis said the more detailed data you have the better understanding you can get of a disease.
“The finer scale the data, the better projections can be made about transmission and severity,” she said.
She said it is particularly difficult when you are looking at large geographic areas.
Smaller scale data can reflect localized behavior and trends in communities, which could help provide a better picture of whether the spread of the virus is happening evenly across Navajo.
“I think chapter level data would be extremely useful in trying to understand where the differences are,” said Lewis. “If you see a much lower severity or rate of infection you can sort out where things are working and what interventions are effective.”
Making sure you have consistent information at the same scale on prevention measures, testing, severity of cases, age distribution, and gender allows for more robust and reliable analysis, she said.
Being able to evaluate things like risk factors and recovery patterns is critical, she added.
“Data also has to be reliable and consistent,” said Lewis. “We want to make sure we’re not comparing apples and oranges.”
Lewis says just looking at the high level case numbers does not tell you much in terms of trends, she said.
Information on contact tracing and case management is also important but her team does not have that data either.
“I’m getting conflicting information on how cases are actually being tracked,” she said.
Finally, Lewis said, there is a lack of information on who gets tested.
For example, they do not know how many people have gone to get tested who were asymptomatic and just wanted to know, or because they had direct contact with someone who was positive, or if they actually had COVID-19 symptoms.
She said a notable fact about the Navajo Epidemiology Center data is that it only includes Navajo citizens who live on the reservation.
If there are Navajo cases living off reservation in border towns like Gallup, those cases are not counted in the Navajo count, but are included in county data instead.
For the same reason, Lewis said she is not sure how accurate the mortality figures are for the Navajo population.
When people who get really sick and are flown to hospitals in cities, she is not sure how they are counted. For example, Lewis said she’s not sure if a Navajo death reported in Albuquerque is tracked back to Navajo or if that registers as a Bernalillo County number.
“It’s a question we haven’t been able to get to the bottom of,” she said.
Chairman Daniel Tso said he would ask the Navajo Epidemiology Department as well as IHS and ’638 providers to share their data with the metals research group.
Challenges with mitigating spread
Until there is a measure of widespread immunity, even when a plateau is reached, it will be fragile, she said.
Not having any idea how many people are carriers is another problem.
“There could be a lot of people infected who are asymptotic contributing to the spread of the virus which makes contact tracing even more important,” she said.
She said the COVID-19 testing is not perfect either and some people are being missed with false negative results.
Lewis said the recommended model of isolation and social distancing for containing the virus goes against the ways Native communities have dealt with stress and crisis in the past.
“It’s counterintuitive to tell a community that’s really highly knit they have to isolate and stay away from each other,” she said. “I think it took longer to adapt that separation.”
Another barrier is the resistance to going to the hospital especially during this time, said Lewis.
“You end up getting people who don’t seek help, which has ripple effects,” she said.
Issues such as lack of running water, personal protective equipment and sanitary supplies have compounded the challenges.
“The need is just so huge,” she said. “It is phenomenal just how difficult it is to get supplies and coordinate distribution. When you think about trying to supply an entire health system for a nation of 170,000, that’s a lot of work.”
Even though there were warnings that a pandemic could hit, the lack of preparedness overall in the country has been exposed through this crisis, said Lewis.
The UNM researchers are Johnnye Lewis, David Begay, Chris Shuey, Li Luo and Daniel Beene.