interim analysis of covid-19 cases in montana (as of 5/1/2020) · cohort is much younger, with a...

MONTANA COMM UNICABLE DISEASE EPIDEMIOLOGY

Reported COVID-19 Cases in Montana as of 5/1/2020

Interim Analysis of COVID-19 cases in Montana (as of 5/1/2020)

This report is an interim epidemiological review of COVID-19 cases in Montana. Data is analyzed based on information available as of May 1, 2020. Current case count at the time of analysis is:

Case Count = 455

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 455 cases of COVID-19 reported in 31 counties in Montana. Gallatin County has been the most impacted, reporting 32% of all reported cases, followed by Yellowstone (18%), Missoula (9%), 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 5/1/2020 1

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Data current as of 5/1/2020

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COVID-19 Cases in Montana by Date of Report and Cumulative Total,2020 [N=455]

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Epidemiological Data A total of 455 cases were reported as of 5/1/2020. 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 (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=455] Data current as of 5/1/2020

The first COVID-19 case in Montana was reported on 3/11/2020. Since then, the number of new cases has climbed to 455 in seven weeks (Figure 3). After reaching the first 100 reported cases within two weeks, well over 100 cases were reported in each of the two following weeks. Since then, every week there have been fewer reported cases than in the previous week. The growth of COVID-19 continues to slow in Montana.

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


~ MONTANA PublicHealth COMM UNICABLE

"ll-lC406 DISEASE EPIDEMIOLOGY

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COVID-19 Laboratory Testing in Montana, 2020 [N=17,962] Data current as of 5/1/2020 800

Private Laboratories

Date

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MTPHL 600 500 400 300 200 100

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~ MONTANA PublicHealth COMMUNICABLE

"ll-lC406 DISEASE EPIDEMIOLOGY

Laboratory 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 implementation 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 17,962 tests have been completed to date. In the most recent week, average of 420 tests were completed daily, which is up from an average of 350 specimens tested every day last week (Figure 4). To date, peak COVID-19 testing volume in Montana occurred on April 2, with a total volume of 719 tests completed.

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

So far 550 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 3.1%. Over time this positivity rate has changed. From March 21st to April 10th, the average positivity was 4% and has dropped by one percent in each subsequent week down to 1% in the most recent week (Figure 5).

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

COVID-19 Laboratory Positive COVID-19 Tests in Montana, 2020 [N=550]

100 90 80 70 60

Q) C)

< 50 40 30 20 10 0

■ Flathead ■ Gallatin ■ Missoula ■ Toole □ Yellowstone □ All Others ■ Montana


Age Distribution for COVID-19 Cases in select Montana Counties, 2020

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

Age Distribution among COVID-19 Patients in Montana [N=455] Data current as of 5/1/2020


Age 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 48 years of age with a range between 1-98 years. Fifty percent of cases are between 31-62 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 53 years old.

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


Data current as of 5/1/2020 Household contact

Cluster 23%

Communityacquired

25%

Contact 15%

HAI <1%

12% Travel associated

25%

Data unavailable and currently under investigation for 9 (2%) persons.

Route of Transmission for COVID-19 cases in Montana, 2020 [N=446]


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 Montana male. Of 450 (99%) cases with known race at the time of report, 94% of persons identify as white and 5% 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 31 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 23% of new case reports, increasing as a more common route of transmission compared to previous weeks (Figure 8).

Race Count Percent White 422 94% American Indian, Alaska Native, Native Hawaiian, Pacific Islander

23 5%

Black or African American

2 0.4%

Asian 1 0.2% Other 2 0.4% TOTAL 450

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


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Transmission over Time for COVID-19 cases in Montana [N=446] Additional data will impact the

Data current as of 5/1/2020 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 no community-acquired cases were reported for a short period of time, but that has changed in the most recent week (Figure 9). Travel-related transmission contributed to most cases early in the outbreak but have declined significantly. This trend held up until recently, when new case reports are attributable to travel again. Contact and particularly cluster investigations have significantly contributed to finding new cases, indicating that disease control efforts through local public health staff is identifying those infected and isolating them appropriately. Though overall new case reports are declining, there has been a change in transmission recently, with new cases likely acquiring the virus through out-of-state travel and in the community.

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


■ ■ ■ ■ ■ ■

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Flathead

Gallatin

Missoula

Toole

Yellowstone

All Others

7 6 9 15

20 49 25 11 33

6 9 7 1 7 9

29

26 25 8 8 15

21 23 19 1 17 40

Cluster Community acquired Contact HAI Household contact Travel associated

Route of known Transmission by select county [N=446]


The five counties with more than 20 reported cases indicate that travel-associated transmission accounts 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

Outcomes The current outcomes of COVID-19 cases in Montana depict the impact of the illness on the population. There are currently 35 (8%) persons actively infected and 404 (89%) 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.


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

Total Reported Cases Recovered and released from isolation Deceased

Outcome of COVID-19 Cases by Age Group [N=455] Data current as of 5/1/2020


Age Distribution by Hospitalization Status COVID-19, Montana [N=450]

■ Not Hospitalized ■ Ever Hospitalized [N=61]

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0

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

Persons who required hospitalization for COVID-19 are generally much older than those not requiring hospitalization (Figure 12). To date, 61 persons have been hospitalized with a median age of 66 years, half of them are between 55 and 77 years old. Those who did not require hospitalization have a median age of 43, and half of patients are between 29 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 infected with COVID-19.

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



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23%

15%

12% 25%

<1%

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Cluster Contact

446**

cases

48.1% of reported COVID-19 cases were identified through contact

tracing and cluster investigations.

2,004 contacts were identified from investigation of 455 COVID-19 cases.

Of cases with the number of identified contacts reported (N=448) an average of 4.4 contacts

were identified for each reported case of COVID-19.

Household contact Community acquired

Healthcare acquired Travel associated

COVID-19 Contact Tracing, Cluster, and Returning Traveler Investigations -- Montana, 2020

Current as of 5/1/2020 at 10:00 pm

This summary provides descriptive epidemiology of reported COVID-19 cases identified through contact tracing and cluster investigation by local public health jurisdictions. Data is subject to change as additional information is received.

Contact Investigations As of May 1, 2020, 455 COVID-19 cases have been reported from 31 counties. Just over 2,000 contacts were identified through case investigation and contact tracing (Figure 1), which highlights the work that local health jurisdictions have done to contain the outbreak in Montana. Close contacts of a COVID-19 case were placed into quarantine and monitored for symptoms daily for two weeks. If a close contact developed any symptoms of COVID-19, they were immediately tested. This process helped contain the COVID-19 outbreak because quarantined individuals that became cases were identified earlier in their illness and were already restricting their exposure to other individuals, resulting in fewer new exposures.

Figure 1. Distribution of COVID-19 cases by likely source of transmission* – Montana, 2020

*Note: Cases could easily be assigned to more than one transmission category; because of this it is possible that some categoriesare underrepresented. **Nine cases remain under investigation.

In Montana’s six largest counties (Cascade, Flathead, Gallatin, Lewis and Clark, Missoula, and Yellowstone), 139 COVID-19 cases were identified as a result of contact tracing. An additional 80 cases were reported in other jurisdictions resulting in a total of 219 cases identified through contact tracing, accounting for nearly half (48%) of all known cases. In many cases, contact tracing helped to identify cases in smaller counties who likely were exposed to individuals in neighboring counties, thus reducing the potential for additional spread (Figure 2).

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Hospitalized

Recovered and released from isolation Recovering

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II I I I

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0%

Contact related Not contact related

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Figure 2. Number and percent of COVID-19 cases attributed to contact tracing by county – Montana, 2020

As reflected in Figure 2, all reported cases in some counties were identified through contact tracing, including Beaverhead, Liberty, Toole, and others. Some counties reported a smaller percentage of cases identified through this process. As an example, two of 15 cases in Cascade County (13%) were attributed to contact tracing; however, 11 of 15 cases were travel-associated (73%) meaning these cases were brought into the county through travel. Of cases identified through contact tracing (N=219), the majority have recovered and been released from isolation (Figure 3).

Figure 3. Current status of cases identified through contact tracing – Montana, 2020 (n=219)

Cluster Investigations As increases in reported COVID-19 cases occurred, contact tracing by local public health identified connections among cases with common exposures. This investigation allowed for the rapid identification and quarantine of

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A B C D E F G H I J K L

M N

7 6

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social event that included 4

contact investigations. 54

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0 25 50 75 100 125 150 175 200 225 Count

Work cases Work contacts Healthcare cases Healthcare contacts Social event cases Social event contacts

Example: Cluster B was part of a

confirmed COVID-19 cases and 8 Clus

ter

Note: not all identified contacts developed symptoms and were tested or identified as cases.

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individuals considered exposed to prevent further spread. A cluster was defined as any setting with three or more associated cases. To date a total of 112 cases have been identified from 14 clusters labelled A-N, with a median of six cases per cluster (Figure 4, darker shading) and an average of 48.6 contacts investigated for each cluster (Figure 4, lighter shading). Seventeen counties have at least one case connected to an identified cluster. Common settings of identified clusters include place of employment (4), healthcare settings (3), and social events (7).

Figure 4. Cases and contacts associated with identified COVID-19 clusters by setting – Montana, 2020

Returning Traveler Notifications Since February 2020, notifications of Montana residents who had travel to an area of widespread COVID-19 activity, or who were exposed to a confirmed COVID-19 case were sent to Montana DPHHS for investigation and follow up by local public health jurisdictions. The majority were identified following air or cruise ship travel to an area of widespread COVID-19 activity. As of May 1, 2020, 435 individuals were followed by local public health to ensure that they were quarantined appropriately and monitored for any development of symptoms (Figure 5). Eight percent were individuals who were mistakenly identified as Montana residents but referred to the correct jurisdiction of residence following local investigation. No known cases were identified in any of these individuals, but all were contacted by local health jurisdictions for follow-up.

Figure 5. Montana residents followed up for potential travel-related COVID-19 exposures – Montana, 2020 (n=435)

5%

84%

3% 8%

435 travelers

Domestic travel International travel

Cruise ship Referred out of state

Counties Reporting at Least One COVID‐19 Case with Trendlines

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

Beaverhead 0 0 0 1 0 0 0 0

Big Horn 0 0 0 0 1 2 0 0

Broadwater 1 0 1 2 0 0 0 0

Carbon 0 0 0 1 5 0 0 0

Cascade 0 0 7 4 2 0 1 1

Deer Lodge 0 0 0 3 0 0 0 0

Fergus 0 0 0 0 0 0 0 1

Flathead 0 2 4 14 14 3 0 0

Gallatin 1 3 42 55 34 7 4 0

Glacier 0 0 0 1 2 1 0 2

Golden Valley 0 0 0 0 1 2 0 0

Hill 0 0 1 0 0 0 0 0

Jefferson 0 0 2 0 0 0 0 0

Lake 1 0 1 3 0 0 0 0

Lewis and Clark 0 3 6 4 3 0 0 0

Liberty 0 0 1 0 0 0 0 0

Lincoln 0 0 3 3 1 0 0 0

Madison 0 1 2 3 2 0 0 0

Meagher 0 0 1 0 0 0 0 0

Missoula 0 4 5 9 11 6 4 0

Musselshell 0 0 0 1 0 0 0 0

Park 0 0 1 5 1 0 0 1

Pondera 0 0 0 0 0 1 1 0

Ravalli 0 1 0 1 1 2 0 0

Richland 0 0 0 0 3 0 0 0

Roosevelt 0 1 0 0 2 3 1 0

Silver Bow 1 0 8 2 0 0 0 0

Stillwater 0 0 0 0 1 0 0 0

Toole 0 0 4 8 8 9 0 0

Wheatland 0 0 0 0 0 0 1 0

Yellowstone 1 4 18 15 19 13 7 5

MONTANA 5 19 107 135 111 49 19 10

‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

_/\__

_/\_

MONTANA COVID-19 CASES

WEEK ENDING 3/13*

WEEK ENDING 4/3

WEEK ENDING 3/27

WEEK ENDING 3/20

WEEK ENDING 4/10

cases reported

counties

55

cumulative cases reported

counties

131 20


counties

24 12


counties

266 23


counties

377 28

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

MT

WY

42.6

96.6

ND 140.0

SD

MONTANA COVID-19 CASES

WEEK ENDING 4/17


counties

426 29

WEEK ENDING 4/24


counties

445 30

WEEK ENDING 5/1


counties

455 31

Case counts based on CDC case reports as of May 1, 2020 and 2019 population estimates from the U.S. Census Bureau

COVID-19 Case Rates Per 100,000 Population

- Montana and neighboring states,

May 1, 2020

Recovered COVID-19 Cases -- Montana, May 1, 2020

30Counties:

1-145Range:

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

404Recovered:

MONTANA COVID-19 CASES COVID-19 Cases by Report Date -- April 18-24, 2020

7Counties:

1-7Range:

19Cases:

COVID-19 Cases by Report Date -- April 25 - May 1, 2020

5Counties:

1-5Range:

10Cases:

Active COVID-19 Cases -- Montana, May 1, 2020 Active: 35

Counties: 14 Range: 1-7

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

interim analysis of covid-19 cases in montana (as of 5/1/2020) · cohort is much younger, with a...

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