interim analysis of covid-19 cases in montana (as of 5/15 ... · interim epidemiological analysis...

IInterim Analysis of COVID-19 cases in Montana (as of 5/15/2020)

This report is an interim epidemiological review of COVID-19 cases in Montana. Data is analyzed based on information available as of May 15, 2020. Current case count at the time of analysis is:

Case Count = 468

This report is completed using data that is available during the time of analysis and there may be a delay between current case count and this report, due to rapidly changing updates. When data is limited to available information, number of cases included in analysis is indicated in graphs.

Geographic Distribution There are 468 cases of COVID-19 reported in 30 counties in Montana. Gallatin County has been the most impacted, reporting 32% of all reported cases, followed by Yellowstone (18%), Missoula (8%), and Flathead (8%) Counties (Figure 1). Most cases are reported in more populous counties. Of the more rural counties, Toole County is particularly impacted by COVID-19, reporting 6% of all COVID-19 cases in Montana.

Figure 1: Map of Reported Montana COVID-19 cases

Interim Epidemiological Analysis for Montana COVID-19 Cases as of 5/15/2020 1

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COVID-19 Cases in Montana by Date of Report and Cumulative Total, 2020 [N=468]

500 Data current as of 5/15/2020

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Epidemiological Data A total of 468 cases were reported as of 5/15/2020. Illness onset date is available for most (97%) reported cases. When onset date is not available, collection date is used to calculate an estimated onset date (Figure 2). Illness onsets that occurred within the past 10 days may not yet be reported, due to a lag time between illness onset, seeking a provider to get tested, and receiving test results.

Figure 2: Epi Curve for Montana COVID-19 cases

COVID-19 Cases in Montana by Date of Illness Onset, 2020 [N=468] Data current as of 5/15/2020

E

The first COVID-19 case in Montana was reported on 3/11/2020. Since then, the number of new cases has climbed to 468 in two months (Figure 3). Growth was initially exponential until reaching about 100 case reports, then growth became linear, meaning the number of new cases each day was about the same as the day before. By mid-April, growth significantly slowed down and in most of May there were few new reported cases. Very recently there has been a slight uptick in case reports.

Figure 3: Cumulative reported cases for COVID-19 in Montana


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COVID-19 Tests 2020 [N=619]45 8%

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LLaboratory Data COVID-19 testing was initially available solely through the CDC. COVID-19 PCR testing capability was implemented by the Montana Public Health Laboratory (MTPHL) on March 9th. Private laboratories began implementing COVID-19 testing in the weeks following. Private laboratories include reference laboratories and those in smaller hospital labs performing point-of-care (POC) testing. A total of 26,106 tests have been completed to date. In May, an average of 580 tests were completed daily, which is up from an average of nearly 400 specimens tested daily in April (Figure 4).

Figure 4: Total Laboratory Testing for COVID-19 in Montana

Montana Public Health Laboratory and Reference Laboratory COVID-19 Tests 2020 [N=26,106]

Date

So far 619 positive tests have been resulted through MTPHL and private laboratories. Some of these tests are repeat specimens from the same individual to check for clearance of the virus, but positive cases are only counted once. The overall positivity rate for all laboratory testing to date is 2%, though this has varied over time. From March 21st to April 10th, the average positivity was 4% and has dropped down to 1%, where it has remained for the last three weeks (Figure 5).

Figure 5: Positive Laboratory Tests for COVID-19 in Montana

Montana Public Health Laboratory and Reference Laboratory Positive

Private Laboratories Positive MTPHL Positive Total Positivity


100

Age Distribution among COVID-19 Patients in Montana [N=468]Data current as of 5/15/2020

92 90 80 70

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AAge and Demographic Distribution Persons between 20-29 years of age account for 20% of all reported COVID-19 cases in Montana. The next most common age group is 50-59 years (18%) followed by those who are 30-39 years (16%) and 60-69 years (16%) (Figure 6). The median age for all cases is 47 years of age with a range between 1-98 years. Fifty percent of cases are between 30-61 years of age.

Figure 6: Age Distribution for COVID-19 cases in Montana

In the five counties with more than 20 reported cases, the age distribution shows some slight variations. Flathead, Gallatin and Yellowstone Counties report ages comparable to the state average with Gallatin County reporting a lower median age and Flathead County a higher median age (Figure 7). Missoula’s cohort is much younger, with a median age of 32 years old. Toole County has the oldest cohort where half of the reported cases are older than 61 years. All other counties have a slightly older age distribution that the state average, with a median age of 52 years old.

Figure 7: Age Distribution for COVID-19 cases in select Montana Counties



T

Persons infected with COVID-19 are nearly equally distributed among men and women, with 52% of cases reported as female and 48% reported as

Table 1: Race of COVID-19 Cases in Montanamale. Of 463 (99%) cases with known race at the time of report, 92% of persons identify as white and 6% as American Indian, Alaska Native, Native Hawaiian or Pacific Islander. Other races making up approximately 1% of the cases identify as African American, Asian or other race (Table 1). Ninety-eight percent of all cases with ethnicity information available identify as non-Hispanic and 2% as Hispanic.

Transmission Characteristics There are 30 counties reporting COVID-19 cases and even though 16 of those counties indicate that at least one person acquired the virus in the community, only five counties report widespread community acquired transmission occurring in their county. Of current data available, 25% of all cases with known transmission information likely acquired the virus in the community; most of those are in Gallatin and Yellowstone Counties. Twenty-five percent of reported cases likely acquired the virus through travel-related exposures. Approximately 27% of cases were contacts to a known case, either within the household or otherwise. Clusters identified 22% of new case reports (Figure 8).

Race Count Percent White 427 92% American Indian, Alaska Native, Native Hawaiian, Pacific Islander

29 6%

Black or African American

2 0.4%

Asian 1 0.2% Other 4 0.9% TOTAL 463

Figure 8: Known Routes of Transmission for Montana COVID-19

Route of Transmission for COVID-19 cases in Montana, 2020 [N=458] Data current as of 5/15/2020Household

contact

Cluster 22%

Communityacquired

25%

Contact 14%

HAI 1%

13% Travel associated

25%

Data unavailable and currently under investigation for 10 (2%) persons.


findings during this time period.

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Community acquired Contact Cluster HAI Household contact Travel associated

CATEGORY DEFINITION

TRAVEL ASSOCIATED Case traveled out-of-state during the incubation period COMMUNITY ACQUIRED Case was unable to be linked with other known cases CONTACT Contact to a case not in their household and not part of a known cluster HOUSEHOLD CONTACT Household contact to a confirmed case CLUSTER Case is part of a known cluster HAI Healthcare-associated infection UNDER INVESTIGATION Likely route of transmission is still under investigation

Transmission changes over time can indicate effective public health efforts, such as timely investigations, thorough contact findings, and measures to reduce community-acquired transmission. Transmission information is generally unknown for newly reported cases under investigation. The percent of community-acquired cases had steadily contributed to disease counts until mid-April, with no new community-acquired cases reported until the end of April, at which point that route of transmission was detected again (Figure 9). Travel-related transmission contributed to most cases early in the outbreak and then declined significantly, contributing to new cases only sporadically for multiple weeks. Now, travel-related cases contribute one third of new reports in May. Contact and particularly cluster investigations have significantly contributed to finding new cases in April, indicating that disease control efforts through local public health staff is identifying those infected and isolating them appropriately. No clusters produced new case reports in May, but household contracts continue to be identified, making up nearly half of all cases reported in May. Though overall new case reports are much lower than in previous weeks, there has been a shift in transmission. Cases are more likely to acquire the virus in a household with a known case. Others appear to get infected through travel and in the community, which is similar to transmission seen earlier in the outbreak.

Figure 9: Percent of known transmission contributing to COVID-19 Montana cases

Transmission over Time for COVID-19 cases in Montana [N=458]Additional data will impact the Data current as of 5/15/2020


The five counties with more than 20 reported cases indicate that travel-associated transmission account for around 20% of cases in Gallatin, Missoula, and Yellowstone Counties and 40% of new cases in Flathead County. About one third of cases in Gallatin and Yellowstone Counties are attributable to community-acquired transmission, whereas in Flathead and Missoula Counties, only about 20% are community-acquired. Contact and household contact investigations contribute to a fair number of new cases in Flathead and Missoula Counties. To date, all cases in Toole County are related to an ongoing cluster of illnesses. In addition, some significant cluster activity is noted in Yellowstone County, as well as some in Gallatin, and Missoula Counties (Figure 10). One third of cases reported in all other counties were travel-related. Another third were either a contact to a known case or household contact. The others were either part of a cluster or acquired the virus in the community.

Figure 10: Breakdown of known transmission for select counties

Route of known Transmission by select county [N=458] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

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Gallatin

Missoula

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Yellowstone

All Others

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Cluster Community acquired Contact HAI Household contact Travel associated

Outcomes The current outcomes of COVID-19 cases in Montana depict the impact of the illness on the population. There are currently 21 (4%) persons actively infected and 431 (92%) persons who have recovered, meaning they have cleared the illness and are released from isolation (Figure 11). Sixteen persons who were infected with COVID-19, have died. The counties reporting deaths are Toole (6), Cascade, (2), Flathead (2), Yellowstone (2), Gallatin (1), Lincoln (1), Madison (1), and Missoula (1). Persons who died were between 52 and 91 years of age, and 56% were male. Twelve (75%) of those who died identified as white and 4 (25%) as Native American.


Figure 11: Current infections and illness outcomes for Montana COVID-19 R

epor

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Outcome of COVID-19 Cases by Age Group [N=468]

100 90 80 70


85827774 74706767

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0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 Age Group

Total Reported Cases Recovered and released from isolation Deceased

Persons who required hospitalization for COVID-19 are generally much older than those not requiring hospitalization (Figure 12). To date, 63 persons have been hospitalized with a median age of 65 years, half of them are between 54 and 76 years old. Those who did not require hospitalization have a median age of 43, and half of patients are between 28 and 58 years old. Native Americans have not been disproportionally infected with the virus in Montana, but complications were more severe in that 30% of Native Americans with COVID-19 required hospitalization versus 13% of those who identify as white and were infected with COVID-19.

Figure 12: Age Distribution among COVID-19 cases compared by known hospitalization status



MONTANA COVID-19 CASES

5 cases reported

5 counties

WEEK ENDING 3/13*

131 cumulative cases reported

20 counties

WEEK ENDING 3/27


12 counties

WEEK ENDING 3/20


23 counties

WEEK ENDING 4/3


28 counties

WEEK ENDING 4/10 *The first case reported in a Montana resident was from Lake county, but they were infected and treated in a different state



29

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WEEK ENDING 4/17


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WEEK ENDING 4/24


30

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WEEK ENDING 5/1


30

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WEEK ENDING 5/8



30

counties

WEEK ENDING 5/15

COVID-19 Case Rates Per 100,000 Population - Montana and neighboring states, May 15, 2020

135.4

249.3

450.7

130.3

43.8

Case counts based on CDC case reports as of May 15, 2020 and 2019 population estimates from the U.S. Census Bureau


Recovered COVID-19 Cases -- Montana, May 15, 2020 431

COVID-19 Cases by Report Date -- May 9-15, 2020

Cases: 10Counties: 5

Range: 1-5

COVID-19 Cases by Report Date -- May 2 - 8, 2020

Cases: 5Counties: 3

Range: 1-3

Recovered:

Counties: 30 Range: 1-145

Recovered COVID-19 includes cases who have recovered and are released from isolation.

Active COVID-19 Cases -- Montana, May 15, 2020 Active: 21

Counties: 9 Range: 1-6

Active COVID-19 includes cases who are hospitalized or recovering but still remain in isolation.

Counties Reporting a COVID‐19 Case with Trendline

County 13 Mar 20 Mar 27 Mar 3 Apr 10 Apr 17 Apr 24 Apr 1 May 8 May 15 May Trend

Beaverhead 0 0 0 1 0 0 0 0 0 0

Big Horn 0 0 0 0 1 2 0 0 0 5

Broadwater 1 0 1 2 0 0 0 0 0 0

Carbon 0 0 0 1 5 0 0 0 0 0

Cascade 0 0 7 4 2 0 1 1 1 1

Deer Lodge 0 0 0 3 0 0 0 0 0 0

Flathead 0 2 4 14 14 3 0 0 0 0

Gallatin 1 3 42 55 34 7 4 0 3 0

Glacier 0 0 0 1 2 1 0 2 0 0

Golden Valley 0 0 0 0 1 2 0 0 0 0

Hill 0 0 1 0 0 0 0 0 0 0

Jefferson 0 0 2 0 0 0 0 0 0 1

Lake 1 0 1 3 0 0 0 0 0 0

Lewis and Clark 0 3 6 4 3 0 0 0 0 0

Liberty 0 0 1 0 0 0 0 0 0 0

Lincoln 0 0 3 3 1 0 0 0 0 0

Madison 0 1 2 3 2 0 0 0 0 0

Meagher 0 0 1 0 0 0 0 0 0 0

Missoula 0 4 5 9 11 6 4 0 0 0

Musselshell 0 0 0 1 0 0 0 0 0 0

Park 0 0 1 5 1 0 0 1 0 0

Pondera 0 0 0 0 0 1 1 0 0 0

Ravalli 0 1 0 1 1 2 0 0 0 0

Richland 0 0 0 0 3 0 0 0 0 0

Roosevelt 0 1 0 0 2 3 1 0 0 0

Silver Bow 1 0 8 2 0 0 0 0 0 0

Stillwater 0 0 0 0 1 0 0 0 0 0

Toole 0 0 4 8 8 9 0 0 0 0

Wheatland 0 0 0 0 0 0 1 0 0 0

Yellowstone 1 4 18 15 19 13 7 4 1 3

MONTANA 5 19 107 135 111 49 19 8 5 10

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interim analysis of covid-19 cases in montana (as of 5/15 ... · interim epidemiological analysis...

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