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title authors authorLinks affiliations date dataset abstract
How to interpret phylogenetic trees
Emma Hodcroft
Nicola Müller
James Hadfield
Sidney M. Bell
Richard Neher
Trevor Bedford
Fred Hutch, Seattle, USA; Biozentrum, Basel, Switzerland; Chan Zuckerberg Initiative, CA, USA
2020 March 13
This narrative explains how to read and interpret the phylogenetic trees that inform genomic epidemiology. This website is optimized for display on desktop browsers.

Table of Contents

How are transmission networks related to phylogenetic trees?

Pathogens spread through rapid replication in one host followed by transmission to another host. An epidemic can only take off when one infection results in more than one subsequent infections.

As the pathogen replicates and spreads, its genome needs to be replicated many times and random mutations (copying mistakes) will accumulate in the genome; this is normal. Such random mutations can help to track the spread of the pathogen and learn about its transmission routes and dynamics.

# An example
<div width="50%" margin="auto">
<p>
<img width="500px" alt="cartoon showing how transmission tree and phylogenetic tree relate" src="https://github.com/nextstrain/nextstrain.org/raw/master/static-site/content/help/01-general/figures/infection_tree_combined.png"/>
</p>
<p>
The illustration above shows a sketch of a transmission tree. Each circle represents a case (infected person), with horizontal lines indicating the duration of their infection. Connected cases represent transmissions from one person to the next.
<br> <br>
Here, we see the full picture of the transmission tree. In practice, however, only a subset of cases are sampled (blue); the transmission tree is unknown and typically only rough estimates of case counts are available. Genome sequences allow us to infer parts of the transmission tree. In this example, three mutations (little diamonds) are indicated on the tree. Sequences that have the same mutations are more closely related, so these mutations allow us to group samples into clusters of closely related viruses that belong to the same transmission chains.
</p>
</div>

How do I read a tree?

The x axis of a tree represents the degree of difference (in time or genetic divergence -- we'll get to that next). The y axis just helps spread things out so we can see everything; it doesn't have any units of measurement.

The tips of the tree represent samples (i.e., blue cases from the last slide). The internal nodes represent cases that weren't sampled, but that we think were the source of all the cases descendant from them (i.e., the red nodes from the last slide). These relationships are inferred by analyzing the pattern of mutations observed in the sampled cases.

## An example
<div width="50%" margin="auto">
<p>
<img width="700px" alt="Example phylogeny where all or only a subset of cases are included in the final phylogeny" src="https://github.com/nextstrain/nextstrain.org/raw/master/static-site/content/help/01-general/figures/toy_alignment_tree.png"/>
</p>
<p>
Above, we see an illustration with a phylogenetic tree on the left, where mutations are shown as colored circles. On the right are the corresponding sequences, also with mutations shown as colored circles. We can see that sequences that share the same mutations group together. When sequences appear linked by a flat vertical line, like A and B, this means there are no differences between them – their sequences are identical.
<br><br>
When a sequence sits on a long line on its own, like C or E, this means it has unique mutations not found in other sequences. The longer the line, the more mutations.
A and B also have unique mutations (the green circle) not shared by the other sequences, but they are identical to each other.
<br><br>
Based on this tree, we would conclude that A & B closely related to each other, and D & E are closely related to each other. A & B are more closely related to C than they are to D & E.
</p>

### Further reading  
* [How to read a tree: tutorial from Arctic Network](https://artic.network/how-to-read-a-tree.html).  
* [How to read a tree: video from Khan academy](https://www.khanacademy.org/science/high-school-biology/hs-evolution/hs-phylogeny/a/phylogenetic-trees).  

</div>

How does the "diversity" panel relate to the tree?

Let's take a look at the first 169 strains of SARS-CoV-2 (the virus that causes COVID-19) that have been publicly shared. Just as on the last page, we built an alignment of these viral sequences (you can see how all of the analyses mentioned here were done on GitHub).

Here we're displaying the phylogenetic tree above a bar-chart showing the variation (i.e. mutations) in the genome. Without these mutations we couldn't build the tree, so the two are intimitely connected.

In this "diversity" panel, the horizontal axis is each site in the viral genome (all thirty thousand or so of them!). The vertical axis indicates how much variability there is at each site.

We've coloured the tree according to one of these mutations -- in this case codon 314 in the gene "ORF1b". There's no a priori reason to think this mutation is a functional mutation (i.e. conferring any biological change). It is precisely mutations such as this which we use to define the relationships between sequences and construct the tree.

Measuring differences with genetic divergence

This is a phylogeny of the first 169 strains of SARS-CoV-2 (the virus that causes COVID-19) that have been publicly shared.

Here, the horizontal axis indicates divergence, which is the number of changes (mutations) in the genome, relative to the root of the tree (i.e., the start of the outbreak). Some sequences may have zero mutations -- meaning they are all identical to the root (center) of the tree. Other viruses have between one and eleven mutations.

At the moment, this may not look much like a ‘tree’. Many of the sequences are identical – they sit together on vertical lines like A and B (some are on the left-most part of the tree). Others have unique or shared mutations and so sit on lines, or ‘branches’, going to the right. You can see how many mutations a branch has by hovering your mouse over it.

Measuring differences over time

We can also visualize how the virus has spread over time by using the sampling date as the x axis. Here, the x axis represents the sampling date of each virus. The tips' positions reflect the date those samples were taken. The dates of internal nodes -- the "missing cases" -- are inferred based on when their descendants were sampled and the rate at which the virus mutates.

Notice how many sequences that previously sat in a line (indicating identical genomes) are now spread apart in time. This happens when the rate at which the virus mutates is slightly slower than the rate at which is spreads. You can scroll up and down between the previous slide and this one, to see how the tree changes.

Dating the start of an outbreak

We can also use genomics to assign a date to when an outbreak started, even if this was before we realized it was happening. Because we can assign dates to each sample and node in the tree, we can use this to infer the date of the 'root' of the tree. This represents the "most recent common ancestor" of all the SARS-CoV-2 sequences we have so far. E.g., your grandparents are the "most recent common ancestors" of you and all of your first cousins.

If you mouse over the leftmost vertical line, you can see that the inferred start date is between mid-November and mid-December of 2019 for this particular outbreak.

How should I interpret traits (colors) on the tree?

Phylogenetic trees often contain additional information, such as the location of each sample collection. From this, we can infer the locations of internal nodes (hypothesized intermediate, unsampled cases) using mathematical models. This can help us understand how the virus is moving from one location to the next.

Interpreting these should, however, be done with caution, as the sampling and sequencing or lack thereof can significantly influence the interpretation.

# An example
<div width="50%" margin="auto">
<p>
<img width="700px" alt="Illustration showing how sampling effects interpretation of viral spread" src="https://github.com/nextstrain/nextstrain.org/raw/master/static-site/content/help/01-general/figures/introductions.png"/>
</p>
<p>
On the left, we show a fully sampled phylogenetic tree, with samples from two different locations denoted by orange and blue. As we walk down the tree, we observe three instances where the color (location) switches from orange to blue. From this, we would conclude that there were three different introductions from the orange location to the blue location.
<br><br>
But, this interpretation relies on sampling: in the middle tree, we've removed one orange sample. We now observe only one switch from orange to blue, suggesting that there was only one introduction into blue that happened much earlier.
<br><br>
In the last example, we have only one sequence from orange, which could lead us to think that there was one introduction from blue into orange.
<br><br>
Thus, while these inferences can be invaluable, they also must be interpreted with caution.
</p>

How does the map relate to the tree?

Here, we show the tree colored by the location of each sample (and inferred location for each internal node). If you click 'Explore the data', you can play an animation of the inferred spread of the virus over the course of the outbreak.

Advanced reading: uncertainty in trees

Earlier, we talked about how internal nodes represent hypothesized unsampled cases. In fact, all trees represent hypotheses about how a pathogen has evolved and moved over time. The trees we present on Nextstrain are point estimates -- that is, the version of this history that maximizes the probability of observing the data that we do.

However, there is always uncertainty in these estimates. Generally speaking, parts of the tree that are densely sampled are more certain; areas that are sparsely sampled are less certain.

# An illustration
<div width="50%" margin="auto">
<p>
<img width="700px" alt="Illustration of the uncertainty inherent in tree reconstruction" src="https://github.com/nextstrain/nextstrain.org/raw/c69bfd0750c284ff12f33682f8d82848e13d9e15/static-site/content/help/01-general/figures/hcov_densitree.png"/>
</p>
</div>

Scientific credit

We would like to acknowledge the amazing and timely work done by all scientists involved in this outbreak, but particularly those working in China. Only through the rapid sharing of genomic data and metadata are analyses such as these possible.



We also gratefully acknowledge GISAID for providing the platform through which these data can be uploaded and shared.


We are grateful for the data gathered by these originating labs:

* Arizona Department of Health Services
* Auckland Hospital
* BCCDC Public Health Laboratory
* Bamrasnaradura Hospital
* Bundeswehr Institute of Microbiology
* CNR Virus des Infections Respiratoires - France SUD
* CR&WISCO GENERAL HOSPITAL
* California Department of Health
* California Department of Public Health
* Center of Medical Microbiology, Virology, and Hospital Hygiene
* Center of Medical Microbiology, Virology, and Hospital Hygiene, University of Duesseldorf
* Centers for Disease Control, R.O.C. (Taiwan)
* Centre for Human and Zoonotic Virology (CHAZVY), College of Medicine University of Lagos/Lagos University Teaching Hospital (LUTH), part of the Laboratory Network of the Nigeria Centre for Disease Control (NCDC)
* Centre for Infectious Diseases and Microbiology - Public Health
* Centre for Infectious Diseases and Microbiology Laboratory Services
* Centro Hospital do Porto, E.P.E. - H. Geral de Santo Antonio
* Centro Hospitalar e Universitario de Sao Joao, Porto
* Charite Universitatsmedizin Berlin, Institute of Virology; Institut fur Mikrobiologie der Bundeswehr, Munich
* Department of Infectious Diseases, Istituto Superiore di Sanita, Roma , Italy
* Department of Infectious and Tropical Diseases, Bichat Claude Bernard Hospital, Paris
* Department of Internal Medicine, Triemli Hospital
* Department of Laboratory Medicine, National Taiwan University Hospital
* Department of Microbiology, Institute for Viral Diseases, College of Medicine, Korea University
* Department of Pathology, Toshima Hospital
* Department of Virology III, National Institute of Infectious Diseases
* Department of Virology and Immunology, University of Helsinki and Helsinki University Hospital, Huslab Finland
* Department of microbiology laboratory,Anhui Provincial Center for Disease Control and Prevention
* Dept. of Pathology, National Institute of Infectious Diseases
* Dept. of Virology III, National Institute of Infectious Diseases
* Dienst Gezondheid & Jeugd Zuid-Holland Zuid
* Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine
* Division of Infectious Diseases, University Hospital Zurich
* Division of Viral Diseases, Center for Laboratory Control of Infectious Diseases, Korea Centers for Diseases Control and Prevention
* Dutch COVID-19 response team
* ErasmusMC
* Foundation Elisabeth-Tweesteden Ziekenhuis
* Foundation Pamm
* Fujian Center for Disease Control and Prevention
* General Hospital of Central Theater Command of People's Liberation Army of China
* Guangdong Provincial Center for Diseases Control and Prevention; Guangdong Provincial Public Health
* Guangdong Provincial Center for Diseases Control and Prevention; Guangdong Provinical Public Health
* Guangdong Provincial Center for Diseases Control and Prevention;Guangdong Provincial Institute of Public Health
* Guangdong Provincial Institution of Public Health, Guangdong Provinical Center for Disease Control and Prevention
* HUS Diagnostiikkakeskus, Hallinto
* Hangzhou Center for Disease Control and Prevention
* Hangzhou Center for Disease and Control Microbiology Lab
* Harborview Medical Center
* Hong Kong Department of Health
* Hospital Israelita Albert Einstein
* IL Department of Public Health Chicago Laboratory
* INMI Lazzaro Spallanzani IRCCS
* Indian Council of Medical Research - National Institute of Virology
* Indian Council of Medical Research-National Institute of Virology
* Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College
* Institute of Viral Disease Control and Prevention, China CDC
* Instituto Nacional de Enfermedades Respiratorias
* KU Leuven, Clinical and Epidemiological Virology
* Klinik Hirslanden Zurich
* Korea Centers for Disease Control & Prevention (KCDC) Center for Laboratory Control of Infectious Diseases Division of Viral Diseases
* Laboratoire National de Sante
* Laboratoire de Virologie, HUG
* Laboratorio di Microbiologia e Virologia, Universita Vita-Salute San Raffaele, Milano
* Laboratory Medicine
* Lapland Central Hospital
* MHC Brabant Zuidoost
* MHC Drente
* MHC Flevoland
* MHC Gooi & Vechtstreek
* MHC Haaglanden
* MHC Kennemerland
* MHC Rotterdam-Rijnmond
* MHC Utrecht
* MHC West-Brabant
* MSHS Clinical Microbiology Laboratories
* Massachusetts Department of Public Health
* Monash Medical Centre
* NHC Key laboratory of Enteric Pathogenic Microbiology, Institute of Pathogenic Microbiology
* National Centre for Infectious Diseases
* National Influenza Center - National Institute of Hygiene and Epidemiology (NIHE)
* National Influenza Centre, National Public Health Laboratory, Kathmandu, Nepal
* National Institute for Viral Disease Control and Prevention, China CDC
* National Public Health Laboratory
* National Public Health Laboratory, National Centre for Infectious Diseases
* Pathology Queensland
* Providence Regional Medical Center
* Public Health Ontario Laboratory
* RIVM
* Respiratory Virus Unit, Microbiology Services Colindale, Public Health England
* Seattle Flu Study
* Serology, Virology and OTDS Laboratories (SAViD), NSW Health Pathology Randwick
* Servicio Microbiologia. Hospital Clinico Universitario. Valencia.
* Shenzhen Key Laboratory of Pathogen and Immunity, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital
* Singapore General Hospital
* Sorbonne Universite, Inserm et Assistance Publique-Hopitaux de Paris (Pitie Salpetriere)
* State Health Office Baden-Wuerttemberg
* Taiwan Centers for Disease Control
* Texas Department of State Health Services
* The Central Hospital Of Wuhan
* The National Institute of Public Health Center for Epidemiology and Microbiology
* The University of Hong Kong - Shenzhen Hospital
* Tianmen Center for Disease Control and Prevention
* UCD National Virus Reference Laboratory
* University of Washington Virology Lab
* Union Hospital of Tongji Medical College, Huazhong University of Science and Technology
* Valley Medical Center
* Virology Department, Sheffield Teaching Hospitals NHS Foundation Trust
* Virology Unit, Institut Pasteur du Cambodge.
* Wales Specialist Virology Centre
* Washington State Department of Health
* Washington State Public Health Lab
* Weifang Center for Disease Control and Prevention
* West of Scotland Specialist Virology Centre, NHSGGC
* Wisconsin Department of Health Services
* Wuhan Fourth Hospital
* Wuhan Jinyintan Hospital
* Wuhan Lung Hospital
* Yongchuan District Center for Disease Control and Prevention
* Zhejiang Provincial Center for Disease Control and Prevention
* Zhongxian Center for Disease Control and Prevention

Detailed scientific credit

These data were shared via GISAID. We gratefully acknowledge their contributions.



To the right we give specific sequences shared by each lab.


The SARS-CoV-2 genomes were generously shared by scientists at these submitting labs:

* Arizona Department of Health Services
	* USA/AZ1/2020

* Auckland Hospital
	* NewZealand/01/2020

* BCCDC Public Health Laboratory
	* Canada/BC_37_0-2/2020

* Bamrasnaradura Hospital
	* Nonthaburi/61/2020
	* Nonthaburi/74/2020

* Beijing Institute of Microbiology and Epidemiology
	* pangolin/Guangdong/P2S/2019
	* pangolin/Guangxi/P1E/2017
	* pangolin/Guangxi/P2V/2017
	* pangolin/Guangxi/P3B/2017
	* pangolin/Guangxi/P4L/2017
	* pangolin/Guangxi/P5E/2017
	* pangolin/Guangxi/P5L/2017

* Bundeswehr Institute of Microbiology
	* Germany/BavPat2/2020
	* Germany/BavPat3/2020

* CNR Virus des Infections Respiratoires - France SUD
	* France/RA739/2020

* CR&WISCO GENERAL HOSPITAL
	* Wuhan/HBCDC-HB-05/2020

* California Department of Health
	* USA/CA3/2020
	* USA/CA4/2020
	* USA/CA5/2020

* California Department of Public Health
	* USA/CA-CDPH-UC1/2020
	* USA/CA-CDPH-UC2/2020
	* USA/CA-CDPH-UC3/2020
	* USA/CA-CDPH-UC4/2020
	* USA/CA-CDPH-UC5/2020
	* USA/CA-CDPH-UC6/2020
	* USA/CA-CDPH-UC7/2020
	* USA/CA-CDPH-UC8/2020
	* USA/CA-CDPH-UC9/2020
	* USA/CA1/2020
	* USA/CA2/2020
	* USA/CA6/2020
	* USA/CA7/2020
	* USA/CA8/2020
	* USA/CA9/2020
	* USA/UC-CDPH-UC11/2020

* Center of Medical Microbiology, Virology, and Hospital Hygiene
	* Germany/NRW-01/2020
	* Germany/NRW-02-1/2020
	* Germany/NRW-03/2020
	* Germany/NRW-04/2020

* Center of Medical Microbiology, Virology, and Hospital Hygiene, University of Duesseldorf
	* Germany/NRW-011/2020
	* Germany/NRW-05/2020
	* Germany/NRW-06/2020
	* Germany/NRW-07/2020
	* Germany/NRW-08/2020
	* Germany/NRW-09/2020
	* Germany/NRW-10/2020

* Centers for Disease Control, R.O.C. (Taiwan)
	* Taiwan/2/2020

* Centre for Human and Zoonotic Virology (CHAZVY), College of Medicine University of Lagos/Lagos University Teaching Hospital (LUTH), part of the Laboratory Network of the Nigeria Centre for Disease Control (NCDC)
	* Nigeria/Lagos01/2020

* Centre for Infectious Diseases and Microbiology - Public Health
	* Australia/NSW10/2020
	* Australia/NSW12/2020
	* Australia/NSW13/2020
	* Australia/NSW14/2020

* Centre for Infectious Diseases and Microbiology Laboratory Services
	* Australia/NSW01/2020
	* Australia/NSW05/2020
	* Australia/NSW06/2020
	* Australia/NSW07/2020
	* Australia/NSW08/2020
	* Australia/NSW09/2020
	* Sydney/2/2020

* Centre for Infectious Diseases and Microbiology- Public Health
	* Australia/NSW11/2020

* Centro Hospital do Porto, E.P.E. - H. Geral de Santo Antonio
	* Portugal/CV62/2020

* Centro Hospitalar e Universitario de Sao Joao, Porto
	* Portugal/CV63/2020

* Charite Universitatsmedizin Berlin, Institute of Virology; Institut fur Mikrobiologie der Bundeswehr, Munich
	* Germany/BavPat1/2020

* Department of Infectious Diseases, Istituto Superiore di Sanita, Roma , Italy
	* Italy/CDG1/2020

* Department of Infectious Diseases, Istituto Superiore di Sanita, Rome, Italy
	* Italy/SPL1/2020

* Department of Infectious and Tropical Diseases, Bichat Claude Bernard Hospital, Paris
	* France/IDF0372-isl/2020
	* France/IDF0372/2020
	* France/IDF0373/2020
	* France/IDF0386-islP1/2020
	* France/IDF0386-islP3/2020
	* France/IDF0515-isl/2020
	* France/IDF0515/2020
	* France/IDF0571/2020

* Department of Internal Medicine, Triemli Hospital
	* Switzerland/1000477102/2020
	* Switzerland/1000477377/2020

* Department of Laboratory Medicine, National Taiwan University Hospital
	* Taiwan/NTU01/2020
	* Taiwan/NTU02/2020
	* Taiwan/NTU03/2020

* Department of Microbiology, Institute for Viral Diseases, College of Medicine, Korea University
	* SouthKorea/KUMC01/2020
	* SouthKorea/KUMC02/2020
	* SouthKorea/KUMC04/2020
	* SouthKorea/KUMC06/2020

* Department of Pathology, Toshima Hospital
	* Japan/TK/20-31-3/2020

* Department of Virology III, National Institute of Infectious Diseases
	* Japan/AI/I-004/2020

* Department of Virology and Immunology, University of Helsinki and Helsinki University Hospital, Huslab Finland
	* Finland/FIN01032020/2020
	* Finland/FIN03032020A/2020
	* Finland/FIN03032020B/2020
	* Finland/FIN03032020C/2020

* Department of microbiology laboratory,Anhui Provincial Center for Disease Control and Prevention
	* Anhui/SZ005/2020

* Dept. of Pathology, National Institute of Infectious Diseases
	* Japan/NA-20-05-1/2020
	* Japan/OS-20-07-1/2020

* Dept. of Virology III, National Institute of Infectious Diseases
	* Japan/KY-V-029/2020
	* Japan/TY-WK-012/2020
	* Japan/TY-WK-501/2020
	* Japan/TY-WK-521/2020

* Dienst Gezondheid & Jeugd Zuid-Holland Zuid
	* Netherlands/Hardinxveld_Giessendam_1364806/2020

* Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine
	* SouthKorea/KUMC03/2020
	* SouthKorea/KUMC05/2020

* Division of Infectious Diseases, University Hospital Zurich
	* Switzerland/1000477796/2020
	* Switzerland/1000477797/2020
	* Switzerland/1000477806/2020

* Division of Viral Diseases, Center for Laboratory Control of Infectious Diseases, Korea Centers for Diseases Control and Prevention
	* SouthKorea/KCDC05/2020
	* SouthKorea/KCDC06/2020
	* SouthKorea/KCDC07/2020
	* SouthKorea/KCDC12/2020
	* SouthKorea/KCDC24/2020

* Dutch COVID-19 response team
	* Netherlands/Gelderland_1/2020
	* Netherlands/Limburg_2/2020
	* Netherlands/Limburg_3/2020
	* Netherlands/Limburg_4/2020
	* Netherlands/Limburg_5/2020
	* Netherlands/Limburg_6/2020
	* Netherlands/NoordBrabant_1/2020
	* Netherlands/NoordBrabant_10/2020
	* Netherlands/NoordBrabant_11/2020
	* Netherlands/NoordBrabant_12/2020
	* Netherlands/NoordBrabant_13/2020
	* Netherlands/NoordBrabant_14/2020
	* Netherlands/NoordBrabant_15/2020
	* Netherlands/NoordBrabant_16/2020
	* Netherlands/NoordBrabant_17/2020
	* Netherlands/NoordBrabant_18/2020
	* Netherlands/NoordBrabant_19/2020
	* Netherlands/NoordBrabant_2/2020
	* Netherlands/NoordBrabant_20/2020
	* Netherlands/NoordBrabant_21/2020
	* Netherlands/NoordBrabant_22/2020
	* Netherlands/NoordBrabant_23/2020
	* Netherlands/NoordBrabant_24/2020
	* Netherlands/NoordBrabant_25/2020
	* Netherlands/NoordBrabant_26/2020
	* Netherlands/NoordBrabant_27/2020
	* Netherlands/NoordBrabant_28/2020
	* Netherlands/NoordBrabant_29/2020
	* Netherlands/NoordBrabant_3/2020
	* Netherlands/NoordBrabant_30/2020
	* Netherlands/NoordBrabant_31/2020
	* Netherlands/NoordBrabant_32/2020
	* Netherlands/NoordBrabant_33/2020
	* Netherlands/NoordBrabant_34/2020
	* Netherlands/NoordBrabant_35/2020
	* Netherlands/NoordBrabant_36/2020
	* Netherlands/NoordBrabant_37/2020
	* Netherlands/NoordBrabant_38/2020
	* Netherlands/NoordBrabant_39/2020
	* Netherlands/NoordBrabant_4/2020
	* Netherlands/NoordBrabant_5/2020
	* Netherlands/NoordBrabant_6/2020
	* Netherlands/NoordHolland_1/2020
	* Netherlands/NoordHolland_2/2020
	* Netherlands/Overijssel_1/2020
	* Netherlands/Overijssel_2/2020
	* Netherlands/Utrecht_1/2020
	* Netherlands/Utrecht_10/2020
	* Netherlands/Utrecht_11/2020
	* Netherlands/Utrecht_12/2020
	* Netherlands/Utrecht_13/2020
	* Netherlands/Utrecht_14/2020
	* Netherlands/Utrecht_15/2020
	* Netherlands/Utrecht_16/2020
	* Netherlands/Utrecht_2/2020
	* Netherlands/Utrecht_3/2020
	* Netherlands/Utrecht_4/2020
	* Netherlands/Utrecht_5/2020
	* Netherlands/Utrecht_6/2020
	* Netherlands/Utrecht_7/2020
	* Netherlands/Utrecht_8/2020
	* Netherlands/ZuidHolland_1/2020
	* Netherlands/ZuidHolland_10/2020
	* Netherlands/ZuidHolland_11/2020
	* Netherlands/ZuidHolland_13/2020
	* Netherlands/ZuidHolland_14/2020
	* Netherlands/ZuidHolland_15/2020
	* Netherlands/ZuidHolland_16/2020
	* Netherlands/ZuidHolland_17/2020
	* Netherlands/ZuidHolland_18/2020
	* Netherlands/ZuidHolland_19/2020
	* Netherlands/ZuidHolland_2/2020
	* Netherlands/ZuidHolland_20/2020
	* Netherlands/ZuidHolland_21/2020
	* Netherlands/ZuidHolland_22/2020
	* Netherlands/ZuidHolland_23/2020
	* Netherlands/ZuidHolland_24/2020
	* Netherlands/ZuidHolland_5/2020
	* Netherlands/ZuidHolland_6/2020
	* Netherlands/ZuidHolland_7/2020
	* Netherlands/ZuidHolland_8/2020
	* Netherlands/ZuidHolland_9/2020

* ErasmusMC
	* Netherlands/Nieuwendijk_1363582/2020
	* Netherlands/Rotterdam_1363790/2020

* Foundation Elisabeth-Tweesteden Ziekenhuis
	* Netherlands/Tilburg_1363354/2020
	* Netherlands/Tilburg_1364286/2020

* Foundation Pamm
	* Netherlands/Berlicum_1363564/2020

* Fujian Center for Disease Control and Prevention
	* Fujian/13/2020
	* Fujian/8/2020

* General Hospital of Central Theater Command of People's Liberation Army of China
	* Wuhan/WH01/2019
	* Wuhan/WH02/2019
	* Wuhan/WH03/2020
	* Wuhan/WH04/2020

* Guangdong Provincial Center for Diseases Control and Prevention; Guangdong Provincial Public Health
	* Foshan/20SF207/2020
	* Foshan/20SF210/2020
	* Foshan/20SF211/2020
	* Guangdong/20SF012/2020
	* Guangdong/20SF013/2020
	* Guangdong/20SF014/2020
	* Guangdong/20SF025/2020
	* Guangdong/20SF028/2020
	* Guangdong/20SF040/2020

* Guangdong Provincial Center for Diseases Control and Prevention; Guangdong Provinical Public Health
	* Guangdong/20SF174/2020
	* Guangzhou/20SF206/2020

* Guangdong Provincial Center for Diseases Control and Prevention;Guangdong Provincial Institute of Public Health
	* Guangdong/20SF201/2020

* Guangdong Provincial Institution of Public Health, Guangdong Provinical Center for Disease Control and Prevention
	* Guangdong/2020XN4239-P0034/2020
	* Guangdong/2020XN4243-P0035/2020
	* Guangdong/2020XN4273-P0036/2020
	* Guangdong/2020XN4276-P0037/2020
	* Guangdong/2020XN4291-P0038/2020
	* Guangdong/2020XN4373-P0039/2020
	* Guangdong/2020XN4433-P0040/2020
	* Guangdong/2020XN4448-P0002/2020
	* Guangdong/2020XN4459-P0041/2020
	* Guangdong/2020XN4475-P0042/2020
	* Guangdong/DG-S2-P0054/2020
	* Guangdong/DG-S41-P0056/2020
	* Guangdong/DG-S6-P0055/2020
	* Guangdong/DG-S9-P0045/2020
	* Guangdong/FS-S29-P0051/2020
	* Guangdong/FS-S30-P0052/2020
	* Guangdong/FS-S34-P0015/2020
	* Guangdong/FS-S42-P0046/2020
	* Guangdong/FS-S48-P0047/2020
	* Guangdong/FS-S50-P0053/2020
	* Guangdong/GD2020012-P0022/2020
	* Guangdong/GD2020016-P0011/2020
	* Guangdong/GD2020080-P0010/2020
	* Guangdong/GD2020085-P0043/2020
	* Guangdong/GD2020086-P0021/2020
	* Guangdong/GD2020087-P0008/2020
	* Guangdong/GD2020115-P0009/2020
	* Guangdong/GD2020134-P0031/2020
	* Guangdong/GD2020139-P0007/2020
	* Guangdong/GD2020227-P0029/2020
	* Guangdong/GD2020233-P0027/2020
	* Guangdong/GD2020234-P0023/2020
	* Guangdong/GD2020241-P0013/2020
	* Guangdong/GD2020246-P0028/2020
	* Guangdong/GD2020258-P0018/2020
	* Guangdong/GDFS2020052-P0025/2020
	* Guangdong/GDFS2020054-P0005/2020
	* Guangdong/GDFS2020056-P0044/2020
	* Guangdong/GDFS2020127-P0026/2020
	* Guangdong/GDSZ202004-P0004/2020
	* Guangdong/GDSZ202008-P0020/2020
	* Guangdong/GDSZ202009-P0032/2020
	* Guangdong/GDSZ202013-P0014/2020
	* Guangdong/GDSZ202015-P0019/2020
	* Guangdong/GZ-S6-P0050/2020
	* Guangdong/JM-S1-P0062/2020
	* Guangdong/MM-S1-P0048/2020
	* Guangdong/SZ-N128-P0057/2020
	* Guangdong/SZ-N59-P0049/2020
	* Guangdong/ZH-N22-P0059/2020
	* Guangdong/ZH-S33-P0058/2020
	* Guangdong/ZQ-S2-P0061/2020
	* Guangdong/ZS-S6-P0060/2020

* HUS Diagnostiikkakeskus, Hallinto
	* Finland/FIN-25/2020

* Hangzhou Center for Disease Control and Prevention
	* Hangzhou/HZCDC0001/2020

* Hangzhou Center for Disease and Control Microbiology Lab
	* Hangzhou/HZ-1/2020

* Harborview Medical Center
	* USA/WA3-UW1/2020
	* USA/WA9-UW6/2020

* Hong Kong Department of Health
	* HongKong/VB20024950/2020
	* HongKong/VB20026565/2020
	* HongKong/VM20001061/2020
	* HongKong/case42_VM20002493/2020
	* HongKong/case48_VM20002507/2020
	* HongKong/case52_VM20002582/2020
	* HongKong/case78_VM20002849/2020
	* HongKong/case85_VM20002868/2020
	* HongKong/case90_VM20002907/2020
	* canine/HongKong/20-02756/2020

* Hospital Israelita Albert Einstein
	* Brazil/SPBR-01/2020
	* Brazil/SPBR-02/2020
	* Brazil/SPBR-03/2020

* Hospital Sao Joaquim Beneficencia Portuguesa
	* Brazil/SPBR-04/2020
	* Brazil/SPBR-05/2020
	* Brazil/SPBR-06/2020

* IL Department of Public Health Chicago Laboratory
	* USA/IL1/2020
	* USA/IL2/2020

* INMI Lazzaro Spallanzani IRCCS
	* Italy/INMI1-cs/2020
	* Italy/INMI1-isl/2020

* Indian Council of Medical Research - National Institute of Virology
	* India/1-27/2020

* Indian Council of Medical Research-National Institute of Virology
	* India/1-31/2020

* Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College
	* Wuhan/IPBCAMS-WH-01/2019
	* Wuhan/IPBCAMS-WH-02/2019
	* Wuhan/IPBCAMS-WH-03/2019
	* Wuhan/IPBCAMS-WH-04/2019
	* Wuhan/IPBCAMS-WH-05/2020

* Institute of Viral Disease Control and Prevention, China CDC
	* Wuhan/IVDC-HB-envF13-20/2020
	* Wuhan/IVDC-HB-envF13-21/2020
	* Wuhan/IVDC-HB-envF13/2020
	* Wuhan/IVDC-HB-envF54/2020

* Instituto Nacional de Enfermedades Respiratorias
	* Mexico/CDMX/InDRE_01/2020

* Jingzhou Center for Disease Control and Prevention
	* Jingzhou/HBCDC-HB-01/2020

* KU Leuven, Clinical and Epidemiological Virology
	* Belgium/GHB-03021/2020

* Klinik Hirslanden Zurich
	* Switzerland/1000477757/2020

* Korea Centers for Disease Control & Prevention (KCDC) Center for Laboratory Control of Infectious Diseases Division of Viral Diseases
	* SouthKorea/KCDC03/2020

* Laboratoire National de Sante
	* Luxembourg/Lux1/2020

* Laboratoire de Virologie, HUG
	* Switzerland/AG0361/2020
	* Switzerland/BL0902/2020
	* Switzerland/GE3121/2020
	* Switzerland/GE3895/2020
	* Switzerland/GE5373/2020
	* Switzerland/GE9586/2020
	* Switzerland/TI9486/2020
	* Switzerland/VD5615/2020

* Laboratorio di Microbiologia e Virologia, Universita Vita-Salute San Raffaele, Milano
	* Italy/UniSR1/2020

* Laboratory Medicine
	* Taiwan/CGMH-CGU-01/2020

* Lapland Central Hospital
	* Finland/1/2020

* MHC Brabant Zuidoost
	* Netherlands/Eindhoven_1363782/2020

* MHC Drente
	* Netherlands/Dalen_1363624/2020

* MHC Flevoland
	* Netherlands/Zeewolde_1365080/2020

* MHC Gooi & Vechtstreek
	* Netherlands/Blaricum_1364780/2020
	* Netherlands/Naarden_1364774/2020

* MHC Haaglanden
	* Netherlands/Nootdorp_1364222/2020

* MHC Hart voor Brabant
	* Netherlands/Oisterwijk_1364072/2020

* MHC Kennemerland
	* Netherlands/Haarlem_1363688/2020

* MHC Rotterdam-Rijnmond
	* Netherlands/Rotterdam_1364040/2020

* MHC Utrecht
	* Netherlands/Utrecht_1363564/2020
	* Netherlands/Utrecht_1363628/2020
	* Netherlands/Utrecht_1364066/2020

* MHC West-Brabant
	* Netherlands/Andel_1365066/2020
	* Netherlands/Helmond_1363548/2020

* MSHS Clinical Microbiology Laboratories
	* USA/NY1-PV08001/2020

* Massachusetts Department of Public Health
	* USA/MA1/2020

* Monash Medical Centre
	* Australia/VIC01/2020

* NHC Key laboratory of Enteric Pathogenic Microbiology, Institute of Pathogenic Microbiology
	* Jiangsu/JS01/2020
	* Jiangsu/JS02/2020
	* Jiangsu/JS03/2020

* National Centre for Infectious Diseases
	* Singapore/12/2020
	* Singapore/13/2020
	* Singapore/14/2020
	* Singapore/3/2020
	* Singapore/4/2020

* National Influenza Center - National Institute of Hygiene and Epidemiology (NIHE)
	* Vietnam/VR03-38142/2020

* National Influenza Centre, National Public Health Laboratory, Kathmandu, Nepal
	* Nepal/61/2020

* National Institute for Viral Disease Control and Prevention, China CDC
	* Beijing/IVDC-BJ-005/2020
	* Chongqing/IVDC-CQ-001/2020
	* Henan/IVDC-HeN-002/2020
	* Jiangsu/IVDC-JS-001/2020
	* Jiangxi/IVDC-JX-002/2020
	* Shandong/IVDC-SD-001/2020
	* Shanghai/IVDC-SH-001/2020
	* Sichuan/IVDC-SC-001/2020
	* Wuhan/IVDC-HB-01/2019
	* Wuhan/IVDC-HB-04/2020
	* Wuhan/IVDC-HB-05/2019
	* Yunnan/IVDC-YN-003/2020

* National Public Health Laboratory
	* Singapore/11/2020

* National Public Health Laboratory, National Centre for Infectious Diseases
	* Singapore/10/2020
	* Singapore/7/2020
	* Singapore/8/2020
	* Singapore/9/2020

* Pathology Queensland
	* Australia/QLD01/2020
	* Australia/QLD02/2020
	* Australia/QLD03/2020
	* Australia/QLD04/2020
	* Australia/QLD09/2020

* Providence Regional Medical Center
	* USA/WA1/2020

* Public Health Ontario Laboratory
	* Canada/ON-PHL2445/2020
	* Canada/ON-VIDO-01/2020

* RIVM
	* Netherlands/Delft_1363424/2020
	* Netherlands/Diemen_1363454/2020
	* Netherlands/Loon_op_zand_1363512/2020
	* Netherlands/Oss_1363500/2020
	* NetherlandsL/Houten_1363498/2020

* Respiratory Virus Unit, Microbiology Services Colindale, Public Health England
	* England/01/2020
	* England/02/2020
	* England/09c/2020
	* England/200641094/2020
	* England/200690245/2020
	* England/200690300/2020
	* England/200690306/2020
	* England/200690756/2020
	* England/200940527/2020
	* England/200960041/2020
	* England/200960515/2020
	* England/200981386/2020
	* England/200990002/2020
	* England/200990006/2020
	* England/200990660/2020
	* England/200990723/2020
	* England/200990724/2020
	* England/200990725/2020
	* England/200991076/2020
	* England/201000003/2020
	* England/201040081/2020
	* England/201040141/2020

* Seattle Flu Study
	* USA/WA-S2/2020
	* USA/WA-S3/2020

* Second Hospital of Anhui Medical University
	* Hefei/2/2020

* Serology, Virology and OTDS Laboratories (SAViD), NSW Health Pathology Randwick
	* Sydney/3/2020

* Servicio Microbiologia. Hospital Clinico Universitario. Valencia.
	* Spain/Valencia1/2020
	* Spain/Valencia2/2020

* Shenzhen Key Laboratory of Pathogen and Immunity, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital
	* Shenzhen/SZTH-002/2020
	* Shenzhen/SZTH-003/2020
	* Shenzhen/SZTH-004/2020

* Shenzhen Third People's Hospital
	* Shenzhen/SZTH-001/2020

* Singapore General Hospital
	* Singapore/1/2020
	* Singapore/2/2020

* Singapore General Hospital, Molecular Laboratory, Division of Pathology
	* Singapore/5/2020
	* Singapore/6/2020

* Sorbonne Universite, Inserm et Assistance Publique-Hopitaux de Paris (Pitie Salpetriere)
	* France/IDF0626/2020

* South China Agricultural University
	* pangolin/Guandong/1/2019

* State Health Office Baden-Wuerttemberg
	* Germany/Baden-Wuerttemberg-1/2020

* Taiwan Centers for Disease Control
	* Taiwan/3/2020
	* Taiwan/4/2020

* Texas Department of State Health Services
	* USA/TX1/2020

* The Central Hospital Of Wuhan
	* Wuhan/HBCDC-HB-02/2020

* The National Institute of Public Health Center for Epidemiology and Microbiology
	* CzechRepublic/951/2020

* The University of Hong Kong - Shenzhen Hospital
	* Shenzhen/HKU-SZ-002/2020
	* Shenzhen/HKU-SZ-005/2020

* Tianmen Center for Disease Control and Prevention
	* Tianmen/HBCDC-HB-07/2020

* UCD National Virus Reference Laboratory
	* Ireland/COR-20134/2020

* UW Virology Lab
	* USA/WA-UW15/2020
	* USA/WA-UW16/2020
	* USA/WA-UW17/2020
	* USA/WA-UW18/2020
	* USA/WA-UW19/2020
	* USA/WA-UW20/2020
	* USA/WA-UW21/2020
	* USA/WA11-UW7/2020
	* USA/WA12-UW8/2020
	* USA/WA13-UW9/2020
	* USA/WA14-UW10/2020
	* USA/WA15-UW11/2020
	* USA/WA16-UW12/2020
	* USA/WA17-UW13/2020
	* USA/WA18-UW14/2020

* Union Hospital of Tongji Medical College, Huazhong University of Science and Technology
	* Wuhan/HBCDC-HB-03/2020
	* Wuhan/HBCDC-HB-04/2020

* Unknown
	* Netherlands/Coevorden_1363618/2020

* Valley Medical Center
	* USA/WA8-UW5/2020

* Virology Department, Sheffield Teaching Hospitals NHS Foundation Trust
	* England/Sheff01/2020
	* England/Sheff02/2020

* Virology Unit, Institut Pasteur du Cambodge.
	* Cambodia/0012/2020

* WA State Department of Health
	* USA/WA1-A12/2020

* Wales Specialist Virology Centre
	* Wales/PHW03/2020
	* Wales/PHW05/2020
	* Wales/PHW1/2020
	* Wales/PHW2/2020

* Washington State Department of Health
	* USA/WA1-F6/2020
	* USA/WA2/2020

* Washington State Public Health Lab
	* USA/WA4-UW2/2020
	* USA/WA6-UW3/2020
	* USA/WA7-UW4/2020

* Weifang Center for Disease Control and Prevention
	* China/WF0001/2020
	* China/WF0002/2020
	* China/WF0003/2020
	* China/WF0004/2020
	* China/WF0006/2020
	* China/WF0009/2020
	* China/WF0012/2020
	* China/WF0014/2020
	* China/WF0015/2020
	* China/WF0016/2020
	* China/WF0017/2020
	* China/WF0018/2020
	* China/WF0019/2020
	* China/WF0020/2020
	* China/WF0021/2020
	* China/WF0023/2020
	* China/WF0024/2020
	* China/WF0026/2020
	* China/WF0028/2020
	* China/WF0029/2020

* West of Scotland Specialist Virology Centre, NHSGGC
	* Scotland/CVR01/2020
	* Scotland/CVR02/2020
	* Scotland/CVR03/2020
	* Scotland/CVR04/2020
	* Scotland/CVR05/2020

* Wisconsin Department of Health Services
	* USA/WI1/2020

* Wuhan Fourth Hospital
	* Wuhan/WH05/2020

* Wuhan Institute of Virology, Chinese Academy of Sciences
	* bat/Yunnan/RaTG13/2013

* Wuhan Jinyintan Hospital
	* Wuhan/HBCDC-HB-01/2019
	* Wuhan/HBCDC-HB-02/2019
	* Wuhan/HBCDC-HB-03/2019
	* Wuhan/HBCDC-HB-04/2019
	* Wuhan/WIV02/2019
	* Wuhan/WIV04/2019
	* Wuhan/WIV05/2019
	* Wuhan/WIV06/2019
	* Wuhan/WIV07/2019

* Wuhan Lung Hospital
	* Wuhan/HBCDC-HB-06/2020

* Yongchuan District Center for Disease Control and Prevention
	* Chongqing/YC01/2020

* Zhejiang Provincial Center for Disease Control and Prevention
	* Zhejiang/WZ-01/2020
	* Zhejiang/WZ-02/2020

* Zhongxian Center for Disease Control and Prevention
	* Chongqing/ZX01/2020