REPORTS

Cite as: X. Deng et al., Science
10.1126/science.abb9263 (2020).

Genomic surveillance reveals multiple introductions of
SARS-CoV-2 into Northern California

1

Department of Laboratory Medicine, University of California, San Francisco, CA, USA. 2UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA,
USA. 3Department of Zoology, University of Oxford, Oxford, UK. 4Lawrence Berkeley National Laboratory, Berkeley, CA, USA. 5California Department of Public
Health, Richmond, CA, USA. 6Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA. 7Fred Hutchinson Cancer Research
Center, Seattle, WA, USA. 8Brotman Baty Institute for Precision Medicine, Seattle, WA, USA. 9Department of Laboratory Medicine, University of Washington,
Seattle, WA, USA. 10Department of Genome Sciences, University of Washington, Seattle, WA, USA. 11Institute for Disease Modeling, Bellevue, WA, USA.
12
Department of Medicine, University of Washington, Seattle, WA, USA. 13Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA.
14
Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA. 15U.S. Centers for Disease Control and Prevention, Atlanta, GA,
USA. 16San Mateo County Department of Public Health, San Mateo, CA, USA. 17Marin County Division of Public Health, San Rafael, CA, USA. 18Solano County
Department of Public Health, Fairfield, CA, USA. 19Sonoma County Department of Public Health, Santa Rosa, CA, USA. 20Sacramento County Division of Public
Health, Sacramento, CA, USA. 21San Joaquin County Department of Public Health, Stockton, CA, USA. 22San Francisco County Department of Public Health, San
Francisco, CA, USA. 23County of Santa Clara, Public Health Department, Santa Clara, CA, USA. 24Department of Medicine, Division of Infectious Diseases,
University of California, San Francisco, CA, USA.
*These authors contributed equally to this work.
†Corresponding author. Email: charles.chiu@ucsf.edu

The COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2 has spread globally, with >52,000
cases in California as of May 4, 2020. Here we investigate the genomic epidemiology of SARS-CoV-2 in
Northern California from late January to mid-March 2020, using samples from 36 patients spanning 9
counties and the Grand Princess cruise ship. Phylogenetic analyses revealed the cryptic introduction of at
least 7 different SARS-CoV-2 lineages into California, including epidemic WA1 strains associated with
Washington State, with lack of a predominant lineage and limited transmission between communities.
Lineages associated with outbreak clusters in 2 counties were defined by a single base substitution in the
viral genome. These findings support contact tracing, social distancing, and travel restrictions to contain
SARS-CoV-2 spread in California and other states.

The novel severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2), which causes coronavirus disease 2019
(COVID-19), is a pandemic that has infected more than 3.2
million people around the world and caused more than
250,000 deaths as of May 4, 2020 (1), including >1.2 million
cases in the United States (US) and >52,000 in California.
An exponential growth in the number of cases has overburdened clinical care facilities and threatens to overwhelm the
medical workforce. The reported case numbers also underestimate the true number of infections due to the limited

First release: 8 June 2020

volume of diagnostic testing to date and the presence of
asymptomatic or mild cases (2–4). As a result, California,
along with many other states and countries, has issued a
“shelter-in-place” policy for all residents, effective March 20,
2020, and ongoing at the time of this report. These unprecedented measures have disrupted daily life significantly for
~40 million inhabitants for an indefinite period, with the
potential for incurring profound economic losses (5).
Until late Feb 2020, the majority of infections identified
in the US were related to travelers returning from high-risk

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Xianding Deng1,2*, Wei Gu1,2*, Scot Federman1,2*, Louis du Plessis3*, Oliver G. Pybus3, Nuno Faria3,
Candace Wang1,2, Guixia Yu1,2, Brian Bushnell4, Chao-Yang Pan5, Hugo Guevara5,
Alicia Sotomayor-Gonzalez1,2, Kelsey Zorn6, Allan Gopez1, Venice Servellita1, Elaine Hsu1,
Steve Miller1, Trevor Bedford7,8, Alexander L. Greninger7,9, Pavitra Roychoudhury7,9,
Lea M. Starita8,10, Michael Famulare11, Helen Y. Chu8,12, Jay Shendure8,9,13, Keith R. Jerome7,9,
Catie Anderson14, Karthik Gangavarapu14, Mark Zeller14, Emily Spencer14, Kristian G. Andersen14,
Duncan MacCannell15, Clinton R. Paden15, Yan Li15, Jing Zhang15, Suxiang Tong15,
Gregory Armstrong15, Scott Morrow16, Matthew Willis17, Bela T. Matyas18, Sundari Mase19,
Olivia Kasirye20, Maggie Park21, Godfred Masinde22, Curtis Chan22, Alexander T. Yu5, Shua J. Chai5,15,
Elsa Villarino23, Brandon Bonin23, Debra A. Wadford5, Charles Y. Chiu1,2,24†

 First release: 8 June 2020

associated with workspace transmission, (iv) 3 samples from
patients who contracted the infection from a sick contacts,(v) 5 samples related to domestic or international travel, and (vi) 7 samples from additional cases of community
transmission.
We performed MSSPE (15) and/or tiled multiplex PCR
(17) on each sample to enrich for the SARS-CoV-2 RNA genome, followed by metagenomic next-generation sequencing
(mNGS) of pooled and indexed samples on Illumina
NextSeq, HiSeq or MiSeq instruments (18, 19). The PCR cycle thresholds ranged from 15.3 to 33.4, corresponding to
virus loads of 1.1 × 104 − 2.7 × 108 copies/mL (fig. S1 and table S2). An average of 31 million (interquartile ratio, IQR,
23-57 million) and 2.2 ± 0.2 million reads were generated
per sample for using MSSPE and tiling multiplex PCR respectively, and virus genomes were assembled by mapping
to reference genome NC_045512 (Wuhan-Hu-1). The assembly yielded 34 SARS-CoV-2 genomes with genome coverage
>65% and these were included in the study. An additional
two genomes sequenced from samples of a returning traveler from Wuhan, China and a household contact collected on
January 29th by the CDC (CA3 and CA4) were also included
in the analysis. The median coverage achieved across all
samples was 97.7% (IQR 90.4.0%-99.7%).
Phylogenetic analysis revealed that the 36 SARS-CoV-2
genomes from California generated in this study were dispersed across the evolutionary tree of SARS-CoV-2 that was
built from 789 worldwide genomes deposited into GISAID
as of March 20, 2020 (Fig. 2A). The 36 genomes included 14
in the Washington State (WA1) lineage, 10 in a lineage associated with the Santa Clara County outbreak cluster (henceforth referred to as the SCC1 lineage), 3 from a Solano
County cluster of 3 individuals, 5 related to lineages circulating in Europe and New York, and 4 related to early lineages from Wuhan or other regions of China (including 2
patients from San Benito County with identical genomes)
(Figs. 1, 2A, and 3 and table S2).
A large outbreak was associated with travel on the US
Grand Princess cruise ship (with at least 78 confirmed positive cases out of 469 tested) as of March 26 (20). The Grand
Princess undertook two consecutive voyages from San Francisco (voyage A to Mexico on February 11 − 21 and voyage B
to Hawaii on February 22 − March 4), with much of the
same crew and a shared subset of passengers. Samples from
11 infected patients were sequenced, 3 of whom had been on
voyage A and became sick after returning to their home
county, and 8 from crew members and passengers aboard
the cruise ship on voyage B. Importantly, all 11 available
sequenced genomes from the Grand Princess were part of
the WA1 lineage (Fig. 2, A and B, and Fig. 3). In addition to
sharing 3 single nucleotide variants (SNVs) that define WA1
(C8782T, C18060T, and T28144C), the sequences from cruise

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countries, repatriated citizens under quarantine, or close
contacts of infected patients. Community spread, in which
the source of the infection is unknown, has since been documented in multiple states. In particular, Washington State
has reported a series of COVID-19 cases from Jan 21 to Mar
18, following the identification of the earliest case reported
in the US, WA1, on Jan 19, suggesting the presence of a persistent transmission chain in the community (6, 7).
Genomic epidemiology of emerging viruses has proven
to be a useful tool for outbreak investigation and for tracking virus evolution and spread (7–9). During the Ebola virus
disease epidemic of 2013-2016 in West Africa, genomic analyses established that the outbreak had a single zoonotic
origin (9), that two major viral lineages were circulating
(10), and that sexual transmission played a role in maintaining some transmission chains (11). Viral genome sequencing
also uncovered the route that Zika virus traveled from
northern Brazil to other regions (12), including Central
America and Mexico (13) and the Caribbean and US (14).
However, real-time genomic epidemiology data of COVID-19
to inform public health interventions in California have
been lacking to date.
We recently developed a method called MSSPE (Metagenomic Sequencing with Spiked Primer Enrichment) to
rapidly enrich and assemble viral genomes directly from
clinical samples (15). Here we used this method and/or tiling multiplex PCR to recover viral genomes from COVID-19
patients in Northern California and perform phylogenetic
analyses to better understand the genetic diversity of SARSCoV-2 in the US and the nature of transmission of virus lineages in the community.
We screened a total of 62 respiratory swab samples
from 54 COVID-19 patients available from hospitals and
clinics at University of California, San Francisco (UCSF), the
California Department of Public Health (CDPH), and 8
county public health departments in Northern California
(table S1). Presumptive positive cases were confirmed to be
SARS-CoV-2 infected by testing using a CDC assay approved
by a Food and Drug Administration (FDA) Emergency Use
Authorization (EUA) on February 4, 2020 (16). SARS-CoV-2
genomes (>65% coverage) were recovered from 36 patients
(Fig. 1A and table S2). The 36 infected patients for whom
viral genomes were obtained were collected from January
29 to March 20, 2020 and spanned 9 counties in Northern
California (Fig. 1B and table S2). The patient samples included (i) 11 samples collected from the Grand Princess
cruise ship, during its two voyages from San Francisco to
Mexico and Hawaii in February and March 2020, (ii) 3 samples from a Solano County cluster that included the first
reported case of community transmission in the US with
subsequent spread to two health care workers, (iii) 7 samples from Santa Clara County from a local outbreak cluster

 First release: 8 June 2020

UC12 fell within a lineage containing many sequences from
European residents or travelers from Europe (Fig. 2A). Interestingly, four additional genomes (UC24, UC26, UC27 and
UC36) were also grouped within the European lineage.
UC27 and UC36 were both diagnosed shortly after returning
to California from New York, consistent with reports that
the New York outbreak that began in March 2020 originated with travelers coming from Europe (21, 22). UC26 also
reported domestic travel from Los Angeles, while UC24 had
no known travel history.
In Santa Clara County, we sequenced 7 genomes from
individuals who were part of a local outbreak of COVID-19
at a large workplace facility with multiple employers, large
areas of shared space, and heavy pedestrian traffic. The genomes all shared the G29711T SNV that defines the SCC1
lineage (Figs. 2C and 3). Four employees (UC13, UC14, UC15,
and UC34) had dates of symptom onset within two weeks of
each other, although they did not know each other. UC16
and UC17 were family members of UC13 and lived in the
same residence, while UC35 transported UC14 to the hospital via emergency medical services. Notably, the genomes
from a Solano county resident (UC21) and a San Mateo couple (UC18 and UC25) were also placed in the SCC1 lineage,
suggesting possible spread to different counties. Further
epidemiological investigation found that UC21 had visited a
merchant in Santa Clara, during which he likely became
infected.
In Solano County, a small cluster of 3 cases included the
first reported instance of community transmission in the US
on February 26 (UC4) (Figs. 2D and 3). The two other cases
(UC2 and UC3) were healthcare workers who were taking
care of patient UC4 and likely contracted the disease in the
hospital, consistent with transmission of the disease from
patient to health care providers (23). The genomic epidemiology of the COVID-19 cases associated with community
spread studied here do not show any predominant SARSCoV-2 lineage circulating in Northern California. In California, multiple recent and unrelated introductions of SARSCoV-2 into the state via different routes appear to give rise
to the diversity of virus lineages reported in this study, with
no single predominant lineage observed. We note that this
does not exclude the possibility of cryptic transmission of
multiple lineages in California simultaneously, as the current level of sampling is not dense enough to confidently
estimate the dates of the seeding events, nor the subsequent
periods of cryptic transmission before a lineage was identified.
There is growing evidence that the WA1 is now an established lineage of SARS-CoV-2 in the US. Here we found
that viruses in the WA1 lineage from Grand Princess cruise
ship passengers as well as from residents of several Northern California counties. In addition, WA1 lineage viruses

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ship passengers and crew also shared two additional SNVs,
C17747T and A17858G common to nearly all WA1 sequences
sampled from Washington and California but not the basal
WA1 case (Figs. 2B and 3).
The WA1 case was reported on January 19 (6), and thus
substantially predated the voyages of the Grand Princess
cruise ship (7, 20). In addition, 6 of 8 passengers on voyage
A (UC 7 −11, 30) carried at least 2 new mutations (G16975T
and C23185T) not observed in UC1, UC19, and UC20, who
were all on the first cruise (Fig. 3). This suggested that the
virus from UC19 could be basally positioned relative to the
cruise ship strains from voyage B, and that COVID-19 infections associated with voyage A may have been passed onto
passengers and crew on voyage B. However, the initial WA1
subtree extracted from the global maximum-likelihood phylogenetic tree did not place UC19 basal to sequences from
voyage B passengers due to artifacts from shared areas of
low coverage (fig. S2). To establish a more accurate tree topology, we therefore reconstructed a new phylogenetic subtree of the WA1 lineage after excluding all ambiguous sites.
In this new subtree (Fig. 2B), UC19 is basal to all other California genomes within the WA1 lineage. In addition, among
the sequences from patients on voyage B, UC5 and UC6
group together, while UC7-11 and UC30 group together with
a sequence sampled in Minnesota.
The chronology and phylogeny of the cruise ship outbreak, along with the predominance of the WA1 lineage in
Washington State (7), suggest that the virus on the Grand
Princess likely came from Washington State, although the
cases may also have originated from a different region in
which the WA1 strain is circulating. In addition to passengers and crew members aboard the Grand Princess, virus
genomes sampled from three cases of community transmission in different counties of the Bay area (UC22, UC23 and
UC28) were also of the WA1 lineage. UC22 was the son of an
infected Grand Princess passenger (UC20) on voyage A and
most likely contracted the virus from household contact.
The UC23 and UC28 cases may also reflect transmission
from disembarking Grand Princess passengers on voyage A,
or pre-existing circulation of the WA1 strain in the community.
Three patients examined in this study (CA3, CA4, and
UC12) had COVID-19 infections associated with international travel or exposure to international travelers. CA3 corresponds to a resident of San Benito County who became sick
shortly after returning from Wuhan, China in late January.
The sequence of his SARS-CoV-2 genome is identical to that
of CA4, a household contact who was also infected with the
virus. Their viral genomes were found to be closely related
to early lineages from China (Fig. 2A and data S1). UC12 had
a prolonged exposure to a known positive traveler from
Switzerland while attending a conference. The genome from

 First release: 8 June 2020

age detected in residents of neighboring San Mateo and
Solano County. Social distancing interventions, such as the
“shelter-in-place” directive that was issued by the governor
of California on March 20, 2020, may assist in stemming
spread from community to community. Interstate dissemination of SARS-CoV-2 lineages has also been demonstrated
coast-to-coast between Washington State and Connecticut
(25), and from domestic and international travel into the
San Francisco Bay Area in the current study. Suspension of
non-essential travel may thus be necessary to prevent ongoing importation of new cases in California and other states.
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have been identified in COVID-19 cases from many states
including Minnesota, Connecticut, Utah, Virginia, and New
York (24, 25). The early date and basal phylogenetic position
of the WA1 virus make it likely that the direction of dissemination was from Washington State to California and other
states; however, this conclusion could change if further genomic sampling in the US revealed additional virus genetic
diversity. Notably, SARS-CoV-2 sequences from Connecticut
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close to the root of the subtree containing the WA1 sequences, raising the possibility that the virus may not have been
first introduced into the US via Washington State.
SARS-CoV-2, like other coronaviruses, contains a nonstructural gene with proofreading activity (26). Consequently, the virus evolves more slowly than many other human
RNA viruses, on the order of 1 to 2 DNA base substitutions a
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Our epidemiological and genomic survey of SARS-CoV-2
has several limitations. First, this initial analysis represents
a relatively sparse sampling of cases. Undersampling of virus genomes is due in part to the high proportion of cases
(80%) with asymptomatic or mild disease (2–4) and limited
diagnostic testing for COVID-19 infection to date in California and throughout the US. Second, the majority of samples
analyzed were obtained from public health laboratories and
thus may not be representative of the general population.
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ACKNOWLEDGMENTS
We acknowledge the help and advice of James T. Lee at the US CDC. We thank all of
the authors who have contributed genome data on GISAID. Author credits for specific GISAID contributions can be found on www.gisaid.org/. Clinical samples from
UCSF were processed according to protocols approved by the UCSF Institutional
Review Board (protocol number 10-01116, 11-05519). Samples collected by the
CDPH were de-identified and deemed not research or exempt by the Committee for
the Protection of Human Subjects (project number 2020-30) issued under the California Health and Human Services Agency’s Federal Wide Assurance #00000681
with the Office of Human Research Protections. A non-research determination for
this project was also granted by Sonoma County as SARS-CoV-2 genome sequencing was designated an epidemic disease control activity, with collected data directly
related to disease control. Funding: This work was funded by NIH grants R33AI129455 (CYC) from the National Institute of Allergy and Infectious Diseases and
K08-CA230156 (WG) from the National Cancer Institute, the California Initiative to
Advance Precision Medicine (CYC), the Charles and Helen Schwab Foundation
(CYC), and the Burroughs-Wellcome CAMS Award (WG). OP and LdP acknowledge
support from the Oxford Martin School and the European Research Council under
the Seventh Framework Program of the European Commission (Pathogen Phylodynamics Grant 614725). Author contributions: CYC conceived, designed, and
supervised the study. AG, AS-G, CW, CYP, GY, HG, VS, and XD performed experiments. CYC, SF, and BB assembled and curated the viral genomes. CYC, WG and XD
analyzed data. CYC, EH, KZ, SM, and WG collected patient samples at UCSF. DM and
GA analyzed genomic and epidemiologic data. TB, AG, PR, LMS, MF, HYC, JS, and
KRJ collected, assembled, and provided viral genome data from Washington and
contributed to the phylogenetic analysis. CA, KG, MZ, ES, and KGA provided viral
genome data from Southern California. CP, JTL, JZ, ST, and YL sequenced and analyzed viral genomes at the CDC. LDP, NF and OP performed phylogenetic analysis of
genomes. AY, BTM, BB, CC, DAW, EV, GM, MP, MW, OK, SC, SM collected samples,
extracted the viral RNA and/or provided epidemiology data from counties in California. CYC, WG, and XD wrote the manuscript. CYC, XD, SF, CW, DAW, LDP, OP, and
WG edited the manuscript. All authors read the manuscript and agree to its contents.
Competing interests: CYC is the director of the UCSF-Abbott Viral Diagnostics and

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Materials and Methods
Figs. S1 and S2
Tables S1 to S5
Data S1
References (31–39)
27 March 2020; accepted 3 June 2020
Published online 8 June 2020
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36. S. Guindon, J.-F. Dufayard, V. Lefort, M. Anisimova, W. Hordijk, O. Gascuel, New
algorithms and methods to estimate maximum-likelihood phylogenies:
Assessing the performance of PhyML 3.0. Syst. Biol. 59, 307–321 (2010).
doi:10.1093/sysbio/syq010 Medline

Discovery Center (VDDC) and receives research support funding from Abbott Laboratories. CYC and XD are inventors on a patent application on the MSSPE method
titled “Spiked Primer Design for Targeted Enrichment of Metagenomic Libraries”
(US Application No. 62/667,344, filed 05/04/2018 by University of California, San
Francisco). HYC is a consultant for Merck and GlaxoSmithKline, and receives research funding from Sanofi-Pasteur, Ellume and Cepheid, unrelated to this work. All
other authors have no conflicts to declare. The opinions expressed by the authors
contributing to this journal do not necessarily reflect the opinions of the Centers for
Disease Control and Prevention or the institutions with which the authors are affiliated. Data and materials availability: Assembled SARS-CoV-2 genomes in this study
were uploaded to GISAID (28, 29) as FASTA files (accession numbers in table S2)
and can be visualized on a continually updated phylogenetic tree on NextStrain (24).
Viral genomes were submitted to the National Center for Biotechnology Information
(NCBI) GenBank database (accession numbers MT419827 – MT419860). Raw sequence data were submitted to the NCBI Sequence Read Archive (SRA) database
(BioProject accession number PRJNA 629889 and umbrella BioProject accession
number PRJNA171119). Locations of SNVs aligned to the reference sequence
(NC_045512), was done by custom scripts (30). This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original
work is properly cited. To view a copy of this license, visit
https://creativecommons.org/licenses/by/4.0/. This license does not apply to
figures/photos/artwork or other content included in the article that is credited to a
third party; obtain authorization from the rights holder before using such material.

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Fig. 1. Genomic survey of SARS-CoV-2 genomes in Northern California. (A) Analysis workflow. (B) Map of the
Northern California survey region divided by county. The pie charts for each county are subdivided according to the
number of patients whose viral genome was sequenced, and the color corresponds to the viral lineage as
determined by phylogenetic analysis. Passengers (n = 3) who were on the Grand Princess cruise ship during voyage
A to Mexico and disembarked to return to their home communities are denoted by a ship icon facing left, while
passengers (n = 8) aboard the Grand Princess cruise ship during voyage B to Hawaii are denoted by a ship icon
facing right. Abbreviations: SCCPHD, Santa Clara County Public Health Department; CDPH, California Department
of Public Health; UCSF, University of California San Francisco; MSSPE, Metagenomic Sequencing with Spiked
Primer Enrichment; NGS, next-generation sequencing.

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8

 Fig. 2 (preceding page). Phylogeny of SARS-CoV-2 lineages in California. (A) Phylogenetic tree of 753
SARS-CoV-2 genomes from GISAID (till Mar 20, 2020) along with the 36 genomes in this survey (tree file
attached in supplementary material). Genomes from Northern California sequenced in the current study
are denoted with colored circles, while other genomes sequenced from California and from other states in
the US are denoted with black and gray circles, respectively. The name of each lineage or outbreak cluster
is shown next to the arc line. (B) Phylogenetic subtree corresponding to the WA1 lineage. This subtree was
reconstructed from 88 SARS-CoV-2 genomes after removal of ambiguous nucleotide sites that had
generated low-coverage artifacts (see text). The WA1 virus from Washington state (first case in the US) is at
the root of the subtree along with a virus sequenced in China. The UC19 virus (from a Grand Princess
voyage A passenger) is basal to the viruses sequenced from crew members and passengers on voyage B.
(C) Zoomed view of the SCC1 lineage associated with the Santa Clara County outbreak cluster. (D) Zoomed
view of the Solano County cluster. The x-axis shows the number of base substitutions relative to the root of
the phylogenetic tree. The key SNVs defining a lineage or cluster are shown in red text. Bootstrap values
(converted from the approximate likelihood ratio test, or aLRT score) are displayed at each node, with a
value of 1 indicating 100% support.

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Fig. 3 (next page). Multiple sequence alignment of all SARS-CoV-2 genomes reported across 9
Northern California counties and the Grand Princess cruise ship. Single nucleotide variants (SNVs) with
respect to the reference genome (NC_045512) are shown as vertical red and black lines for lineage defining
SNVs and other SNVs, respectively. Cases that are part of the WA1 lineage include the first case of COVID19 infection (WA1) in the US, 8 passengers and crew members aboard the Grand Princess cruise ship
during its second trip (voyage B), and 3 individuals surveyed from 3 Northern California counties as
passengers on the ship’s first trip (voyage A). The three SNVs C8782T, C18060T, and T28144C define the
WA1 lineage, and the two SNVs C17747T, A17858G are common to Grand Princess passengers and crew.
Viruses from voyage B passengers and crew share SNVs G16975T and C23185T that are lacking in viruses
from voyage A passengers. Single SNV variants C9924T and G29711T define the lineages from Solano
County and Santa Clara County, respectively. The putative epidemiological link and sample collection date
are shown beside the sequence alignment.

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 Genomic surveillance reveals multiple introductions of SARS-CoV-2 into Northern California
Xianding Deng, Wei Gu, Scot Federman, Louis du Plessis, Oliver G. Pybus, Nuno Faria, Candace Wang, Guixia Yu, Brian Bushnell,
Chao-Yang Pan, Hugo Guevara, Alicia Sotomayor-Gonzalez, Kelsey Zorn, Allan Gopez, Venice Servellita, Elaine Hsu, Steve Miller,
Trevor Bedford, Alexander L. Greninger, Pavitra Roychoudhury, Lea M. Starita, Michael Famulare, Helen Y. Chu, Jay Shendure,
Keith R. Jerome, Catie Anderson, Karthik Gangavarapu, Mark Zeller, Emily Spencer, Kristian G. Andersen, Duncan MacCannell,
Clinton R. Paden, Yan Li, Jing Zhang, Suxiang Tong, Gregory Armstrong, Scott Morrow, Matthew Willis, Bela T. Matyas, Sundari
Mase, Olivia Kasirye, Maggie Park, Godfred Masinde, Curtis Chan, Alexander T. Yu, Shua J. Chai, Elsa Villarino, Brandon Bonin,
Debra A. Wadford and Charles Y. Chiu

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REFERENCES

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