Introduction and Epidemiology

Introduction

In late 2019 a new respiratory illness appeared in Wuhan, China caused by SARS-CoV-2, a betacoronavirus similar to SARS and MERS, both of which originated in bats. The respiratory illness, coronavirus disease-19 (COVID-19) expanded rapidly and now represents an evolving public health emergency with new information published daily. Some of the information presented here may later be shown to be incorrect as our understanding of COVID-19 expands. Facebook, Twitter, and other social media sites are NOT reliable sources of information. Please use the resources listed on the opening page of this website to stay updated during the current COVID-19 outbreak.

What is COVID-19?

SARS-CoV-2 belongs to family of viruses that cause a broad range of symptoms, ranging from the common cold to more severe infections. These viruses are large, enveloped, positive-sense single-stranded RNA viruses.1 Previous coronavirus outbreaks causing severe disease include severe acute respiratory syndrome (SARS-CoV; 2002–2003) and the Middle Eastern respiratory syndrome coronavirus (MERS-CoV; 2012–present).

Coronaviruses that cause the common cold are commonplace and widespread, accounting for 10% to 30% of upper respiratory tract infections in adults. The incidence of these infections increases during the winter months. Laboratory tests that detect these pervasive coronaviruses are not able to detect SARS-CoV-2.1

Epidemiology

Where and when was COVID-19 first detected?

On December 30, 2019, a cluster of pneumonia cases of unknown etiology in Wuhan, China was reported to Chinese public health authorities. Most cases reported an exposure to the Wuhan seafood market, which was closed on January 1, 2020.2 A novel coronavirus was first reported on January 7, and the first fatal case occurred on January 11. The first case outside of China was reported in Thailand on January 13,3 and the first U.S. case was reported on January 20.3 Initially, all cases reported outside of China were in returning travelers from Wuhan province.2

Which countries/regions are affected by the current outbreak?

WHO: Reported Cases of COVID-19 as of July 8 (by WHO Region)
Total (new cases in last 24 hours)

Region Cases Deaths
Globally 11,669,259 (168,957) 539,906 (4,147)
Africa 397,942 (15,379) 7,415 (276)
Americas 6,004,685 (89,134) 268,828 (2,092)
Eastern Mediterranean 1,204,698 (17,078) 28,664 (562)
Europe 2,827,789 (17,941) 201,255 (604)
South-East Asia 1,001,655 (27,266) 26,224 (605)
Western Pacific 231,749 (2,159) 7,507 (8)
Source: WHO: COVID-19 Situation Report – 170
Figure 1. Number of confirmed COVID-19 cases reported in the last seven days by country, territory, or area – as of July 8. (source: https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200708-covid-19-sitrep-170.pdf).

The United States has assisted with voluntary evacuations of U.S. citizens from China, and the U.S. Centers for Disease Control and Prevention (CDC) has issued travel risk assessments.

How many cases of COVID-19 are there? How many patients have died?

As of July 8, there were 11,669,259 confirmed cases of COVID-19 with 539,906 deaths reported.4 The case fatality rate (CFR) is estimated to be between 0.6% (South Korea) and 5.0% (Italy).4 There are several caveats that make it difficult to determine what the most accurate CFR is at this time. On the one hand, many of the recently reported cases remain sick, with some in critical care, so there is a lag between reporting of cases and clinical outcome, which could increase the CFR. On the other hand, case detection has focused on patients with clinically significant and severe illness, so patients with mild symptoms or without symptoms may not be recognized which could result in a higher computed CFR. In general, countries with aggressive case-finding measures (such as South Korea) report a CFR that is lower than that for countries with more limited testing capacity (including the US as of March 9th).

The total number of cases is higher than occurred in the SARS-CoV and MERS-CoV outbreaks.5 The case fatality rate (CFR) and percentage of patients with severe disease are both lower than reported for SARS-CoV and MERS-CoV. For comparison, 774/8098 (9.6%) of patients with SARS-CoV died, and 858/2494 (34.4%) of patients with MERS-CoV died.5

With rapid evolution of guidance, we are making syndicated content in this section provided and maintained by the CDC

Source: CDC – Coronavirus Disease 2019 (COVID-19) in the U.S.

Texas and Harris County COVID-19 cases

Texas COVID-19 Reported Cases – July 8

Total state-wide cases: 220,564 ; Deaths: 2,813

County of Residenceb Casesc Deaths
Harris 39,311 407
Dallas 28,131 410
Bexar 15,880 137
Tarrant 15,585 248
Travis 12,408 151
El Paso 8,035 144
Hidalgo 5,447 75
Galveston 4,809 50
Nueces 4,472 27
Fort Bend 4,346 59
Collin 3,825 50
Denton 3,459 37
Hays 3,243 10
Williamson 3,151 45
Jefferson 3,094 36
Lubbock 3,051 56
Brazoria 3,036 23
Potter 3,008 39
Cameron 2,997 70
Montgomery 2,654 38
Brazos 2,626 34
Walker 2,149 28
Webb 2,091 32
McLennan 2,044 13
Bell 1,734 13
Ellis 1,351 19
Victoria 1,334 9
Anderson 1,152 3
Smith 1,098 5
Midland 976 19
Randall 971 7
Ector 946 11
Moore 909 15
Guadalupe 901 3
Kaufman 874 5
Starr 843 4
Titus 843 6
Comal 750 9
Johnson 737 4
Grayson 688 5
Gregg 652 13
Bastrop 619 7
Grimes 617 2
Hunt 616 8
Jones 611
Angelina 610 9
Tom Green 595 1
Hale 592 7
Taylor 573 6
Maverick 550 5
Caldwell 539 3
Wichita 512 3
Nacogdoches 479 29
Parker 473 1
Bowie 467 15
Chambers 454 2
Liberty 445 3
Rockwall 420 16
Orange 415 5
Navarro 396 6
Harrison 389 31
Val Verde 387 1
Deaf Smith 383 17
Coryell 353 2
Lamar 347 13
Medina 335 3
Washington 333 32
Gonzales 314 4
Hardin 303 5
Rusk 292 3
Shelby 288 11
Matagorda 286 5
Cherokee 270 2
Wharton 251 1
Willacy 243 3
Frio 239
Jim Wells 230
Parmer 229 8
Panola 218 24
Henderson 215 4
Polk 205
Waller 205
San Patricio 204
Burnet 203 3
Lavaca 198 1
Erath 186 1
Uvalde 179 1
Houston 174
Wise 157 5
Hood 154 5
Atascosa 152 2
Van Zandt 150 3
Brewster 147 1
Wilson 146 5
Pecos 135 1
Fayette 134 3
Camp 128 2
Gray 126 4
Fannin 122 8
Andrews 120 2
Burleson 120
Milam 120 1
Brown 117 13
Hill 117 2
Red River 117 12
Kerr 115 1
Wood 115 5
San Augustine 114 7
Calhoun 113 3
Colorado 111
DeWitt 110 3
Bailey 109 1
Castro 107 1
Kleberg 106 1
Austin 105
Dallam 104 1
Bee 98
Hockley 96 1
Kendall 95
Lee 88 3
Hopkins 78
Leon 78
Upshur 78
Robertson 77
Cooke 75
Madison 75
Limestone 74 1
Lamb 71
Scurry 71 1
Dawson 70 1
Hutchinson 70
Jasper 69 1
Jackson 68 1
Duval 67
San Jacinto 64
Zapata 63
Crane 62 9
Live Oak 62
Howard 60 1
Karnes 60
Ochiltree 60 2
Freestone 59
Reeves 59 1
Franklin 53
Gillespie 53
Cass 52 2
Palo Pinto 52 2
Blanco 49 1
Floyd 49
Morris 49
Nolan 49
Trinity 48
Aransas 46
Lynn 45 1
Swisher 45 1
Falls 44
Terry 44
La Salle 41
Hartley 40 2
Yoakum 40
Winkler 38
Young 38 1
Marion 37 1
Refugio 37
Gaines 36
Mason 35
Bosque 33
Hansford 31 2
Crosby 30 1
Lampasas 30
Sherman 30
Tyler 30
Ward 29
Zavala 29
Donley 28
Sabine 28 1
Bandera 27
Hamilton 26 1
Callahan 25 2
Comanche 25 1
Jim Hogg 25
Llano 24
Montague 24 1
McCulloch 22
Martin 21 1
Schleicher 21 1
Somervell 20
Presidio 19
Wheeler 19
Brooks 18
Dimmit 18
Garza 18
Mitchell 18
Hemphill 17
Runnels 17
Crockett 16
Hudspeth 16
Rains 16
Wilbarger 16
Goliad 15
Reagan 15
Clay 13
Eastland 13
Sutton 13
Jack 12
Menard 12
Newton 12
Archer 11
Concho 11
Fisher 11 1
Lipscomb 11
Stephens 11
Kimble 9
Briscoe 8
Carson 7
Childress 7
Delta 7
San Saba 7
Upton 7
Collingsworth 6
Glasscock 6
Haskell 6
Roberts 6
Coke 5 1
Hardeman 5
Knox 5
Shackelford 5
Cochran 4
Coleman 4
Cottle 4 1
Culberson 4
Jeff Davis 4
Oldham 4 1
Real 4
Armstrong 3
Mills 3
Dickens 2
Edwards 2
Hall 2 1
Irion 2
Kinney 2
Motley 2
Terrell 2
Baylor 1
Kenedy 1
Throckmorton 1
Borden 0
Foard 0
Kent 0
King 0
Loving 0
McMullen 0
Sterling 0
Stonewall 0
Total Statewide 220564 2813
  1. DSHS will update the state case count each day by noon Central Time.
  2. Patient may be undergoing treatment in facilities in other counties
  3. Does not include repatriation cases.
Source: Texas Health and Human Services

The Centers for Disease Control and Prevention (CDC) has confirmed multiple cases of novel coronavirus 2019 in people under federal quarantine at the Joint Base San Antonio-Lackland. The first was a traveler who returned on a U.S. State Department-chartered flight from Wuhan City, China. The others returned on a State Department flight for passengers from the Diamond Princess cruise ship quarantined in Yokohama, Japan. Most of the travelers have completed their quarantine period and returned home. Some individuals who tested positive will remain isolated until they test negative for the virus and are no longer at risk of spreading it. The CDC has the latest information on the number of people under quarantine who are infected and is updating its national numbers each Monday, Wednesday, and Friday. Those cases are not included in the Texas case count.

How does COVID-19 spread?

Person-to-person transmission is likely the most common means of transmission.6,7 Based on how other coronaviruses spread, droplet transmission is presumed. Recent articles have found evidence that the virus can be detected in stool, suggesting that contact precautions and good handwashing are warranted.8,9 It remains unknown if fomites can transmit the virus.

Case reports suggest that the virus can be transmitted by patients who are asymptomatic or who have mild symptoms.

Transmission to healthcare workers was a key feature of the SARS-CoV epidemic during 2002–2003. A case series of 138 hospitalized patients with COVID-19 in Wuhan found that hospital-associated transmission was suspected as the presumed mechanism of transmission in 40 (29%) affected health professionals and in 17 (12.3%) affected patients.10

One measure of a pathogen’s ability to spread is the basic reproductive number, also known as R0 (R-naught). This number is an estimate of the average number of people to whom one person infected with the pathogen transmits the disease. For example, an R0 of 2.0 means that each person with the disease infects two new people.

The R0 for COVID-19 has been estimated at 2.2–3.6 in one study11 and 2.2 in another.7 A recent metanalysis found that the median R0 from modeling studies was 2.8, with an interquartile range of 1.6-4.0.12 As we continue to identify cases and our understanding of this virus expands, this number may change. This estimate is higher than the R0 value for MERS-CoV (<1.0)6 and is similar to the R0 value for SARS-CoV (2.0–5.0).6 For comparison, the R0 for pandemic influenza (2009 H1N1) was estimated to be 1.2–2.3.13

An important epidemiologic phenomenon during the SARS-CoV outbreak was “superspreaders” — individuals with the disease who infected a much larger number of people than the R0 for SARS-CoV. It is unknown if this phenomenon will similarly affect the transmission dynamics of COVID-19.

References

  1. Paules CI, Marston HD, Fauci AS. Coronavirus Infections—More Than Just the Common Cold. JAMA. 2020;37(October):435. doi:10.1001/jama.2020.0757
  2. Wang C, Horby PW, Hayden FG, Gao GF. A novel coronavirus outbreak of global health concern. Lancet. 2020;6736(20):1-4. doi:10.1016/S0140-6736(20)30185-9
  3. Holshue ML, DeBolt C, Lindquist S, et al. First Case of 2019 Novel Coronavirus in the United States. N Engl J Med. January 2020:NEJMoa2001191. doi:10.1056/NEJMoa2001191
  4. WHO. Coronavirus disease 2019. World Heal Organ. 2020;2019(March):2633. doi:10.1001/jama.2020.2633
  5. Mahase E. China coronavirus: what do we know so far? BMJ. 2020;368(January):m308. doi:10.1136/bmj.m308
  6. Fuk-Woo Chan J, Yuan S, Kok K-H, et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster. Lancet. 2020;6736(20):1-10. doi:10.1016/S0140-6736(20)30154-9
  7. Li Q, Guan X, Wu P, et al. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia. N Engl J Med. 2020:1-9. doi:10.1056/NEJMoa2001316
  8. Gu J, Han B, Wang J. COVID-19: Gastrointestinal manifestations and potential fecal-oral transmission. Gastroenterology. 2020. doi:10.1053/j.gastro.2020.02.054
  9. Xiao F, Tang M, Zheng X, et al. Evidence for gastrointestinal infection of SARS-CoV-2. medRxiv. 2020:2020.02.17.20023721. doi:10.1101/2020.02.17.20023721
  10. 10Wang D, Hu B, Hu C, et al. Clinical Characteristics of 138 Hospitalized Patients with 2019 Novel Coronavirus-Infected Pneumonia in Wuhan, China. JAMA - J Am Med Assoc. 2020:1-9. doi:10.1001/jama.2020.1585
  11. Zhao S, Lin Q, Ran J, et al. Preliminary estimation of the basic reproduction number of novel coronavirus (2019-nCoV) in China, from 2019 to 2020: A data-driven analysis in the early phase of the outbreak. Int J Infect Dis. 2020;243:153057. doi:10.1016/j.ijid.2020.01.050
  12. Liu Y, Gayle AA, Wilder-Smith A, Rocklöv J. The reproductive number of COVID-19 is higher compared to SARS coronavirus. J Travel Med. 2020;(Figure 1):1-4. doi:10.1093/jtm/taaa021
  13. Boëlle PY, Ansart S, Cori A, Valleron AJ. Transmission parameters of the A/H1N1 (2009) influenza virus pandemic: A review. Influenza Other Respi Viruses. 2011;5(5):306-316. doi:10.1111/j.1750-2659.2011.00234.x
* On February 11, 2020, the World Health Organization named the novel coronavirus disease “COVID-19”. The agent responsible for COVID-19 is the novel coronavirus, SARS-CoV-2.