genomic sequencing
South Africa Study Shows Power of Genomic Surveillance Amid COVID-19 Pandemic
Posted on by Dr. Francis Collins
Considerable research is underway around the world to monitor the spread of new variants of SARS-CoV-2, the coronavirus that causes COVID-19. That includes the variant B.1.351 (also known as 501Y.V2), which emerged in South Africa towards the end of 2020 [1, 2]. Public health officials in South Africa have been busy tracing the spread of this genomic variant and others across their country. And a new analysis of such data reveals that dozens of distinct coronavirus variants were already circulating in South Africa well before the appearance of B.1.351.
A study of more than 1,300 near-whole genome sequences of SARS-CoV-2, published recently in the journal Nature Medicine, shows there were in fact at least 42 SARS-CoV-2 variants spreading in South Africa within the pandemic’s first six months in that country [3]. Among them were 16 variants that had never before been described. Most of the single-letter changes carried by these variants didn’t change the virus in important ways and didn’t rise to significant frequency. But the findings come as another critical reminder of the value of genomic surveillance to track the spread of SARS-CoV-2 to identify any potentially worrisome new variants and to inform measures to get this devastating pandemic under control.
SARS-CoV-2 was first detected in South Africa on March 5, 2020, in a traveler returning from Italy. By November 2020, despite considerable efforts to slow the spread, more than 785,000 people in South Africa were infected, accounting for about half of all reported COVID-19 cases on the African continent.
Recognizing the importance of genomic surveillance, researchers led by Houriiyah Tegally and Tulio de Oliveira, University of KwaZulu-Natal, Durban, South Africa, wasted no time in producing 1,365 near-complete SARS-CoV-2 genomes by mid-September, near the end of the coronavirus’s first peak in the country. Those samples had been collected in hundreds of clinics over the course of the pandemic in eight of South Africa’s nine provinces, offering a broad picture of the spread and emergence of new variants across the country.
The data revealed three main variants, dubbed B.1.1.54, B.1.1.56, and C.1, that were responsible for 42 percent of all the infections in South Africa’s first wave. Of the 16 newly described variants, most carried single-letter changes that haven’t been identified in other countries.
The majority of changes were what scientists refer to as “synonymous,” meaning that they don’t change the structure or function of any of the virus’s essential proteins. The exception is the newly identified C.1, which includes 16 single-letter changes compared to the original sequence from Wuhan, China. One of those 16 changes swaps a single amino acid for another on SARS-CoV-2’s spike protein. That’s notable because the spike protein is a key target of antibodies and also is essential to the virus’s ability to infect human cells.
In fact, four of the most prevalent variants in South Africa all carry this same mutation. The researchers also saw three other changes that would alter the spike protein in different ways, although the significance of these for viral spread and our efforts to stop it isn’t yet clear.
Importantly, the data show that the bulk of introductions to South Africa happened early on, before lockdown and travel restrictions were implemented in late March. Subsequently, much of the spread within South Africa stemmed from hospital outbreaks. For example, an outbreak of the C.1 variant in the North West Province in April ultimately led this variant to become the most geographically widespread in South Africa by the end of August. Meanwhile, an earlier identified South African-specific variant, B.1.106, first identified in April, vanished altogether after outbreaks were controlled in KwaZulu-Natal Province, where the researchers reside.
Genomic surveillance has remarkable power for understanding the evolution of SARS-CoV-2 and tracking the dynamics of its transmission. Tegally and de Oliveira’s team notes that this type of intensive genomic surveillance now can be used on a large scale across Africa and around the world to identify new variants of SARS-CoV-2 and to develop timely measures to control the spread of the virus. They’re now working with the African CDC to expand genomic surveillance across Africa [4].
Such genomic surveillance was crucial in the subsequent identification of the B.1.351 variant in South Africa that we’ve been hearing so much about, with its potential to evade our current treatments and vaccines. By picking up on such concerning mutations early through genomic surveillance and understanding how the virus is spreading over time and space, the hope is we’ll be better informed and more adept in our efforts to get this pandemic under control.
References:
[1] Emerging SARS-CoV-2 variants. Centers for Disease Control and Prevention.
[2] Emergence and rapid spread of a new severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) lineage with multiple spike mutations in South Africa. Tegally H, Wilkinson E, Giovanetti M, Iranzadeh A, Bhiman J, Williamson C, de Oliveira T, et al. medRxiv 2020 Dec 22.
[3] Sixteen novel lineages of SARS-CoV-2 in South Africa. Tegally H, Wilkinson E, Lessells RJ, Giandhari J, Pillay S, Msomi N, Mlisana K, Bhiman JN, von Gottberg A, Walaza S, Fonseca V, Allam M, Ismail A, Glass AJ, Engelbrecht S, Van Zyl G, Preiser W, Williamson C, Petruccione F, Sigal A, Gazy I, Hardie D, Hsiao NY, Martin D, York D, Goedhals D, San EJ, Giovanetti M, Lourenço J, Alcantara LCJ, de Oliveira T. Nat Med. 2021 Feb 2.
[4] Accelerating genomics-based surveillance for COVID-19 response in Africa. Tessema SK, Inzaule SC, Christoffels A, Kebede Y, de Oliveira T, Ouma AEO, Happi CT, Nkengasong JN.Lancet Microbe. 2020 Aug 18.
Links:
COVID-19 Research (NIH)
Houriiyah Tegally (University of KwaZulu-Natal, Durban, South Africa)
Tulio de Oliveira (University of KwaZulu-Natal)
Uncovering a Hidden Zika Outbreak in Cuba
Posted on by Dr. Francis Collins
When Brazilian health officials discovered four years ago that the mosquito-borne Zika virus could cause severe birth defects and other serious health problems, it prompted a major effort across the Americas to curb the infection by controlling mosquitoes and issuing travel advisories. By mid-2017, the hard work seemed to have paid off, and reports of new Zika infections had nearly stopped.
But it turns out Zika may be tougher to control than once thought. New research shows that a large, previously hidden outbreak of Zika virus disease occurred in Cuba, just when it looked like the worst of the epidemic was over. The finding suggests that the Zika virus can linger over long periods, and that mosquito control efforts alone may slow, but not necessarily stop, the march of this potentially devastating infectious disease.
When combating global epidemics, it’s critical to track the spread of dangerous viruses from one place to the next. But some viruses can be tougher to monitor than others, and that certainly has been the case with Zika in the Americas. Though the virus can harm unborn children, many people infected with Zika never feel lousy enough to go to the doctor. Those who do often have symptoms that overlap with other prevalent tropical diseases, such as dengue and chikungunya fever, making it hard to recognize Zika.
That’s why in Brazil, where Zika arrived in the Americas by early 2014, this unexpected viral intruder went undetected for well over a year. By then, it had spread unnoticed to Honduras, circulating rapidly to other Central American nations and Mexico—likely by late 2014 and into 2015.
In the United States, even with close monitoring, a small local outbreak of Zika virus in Florida also went undetected for about three months in 2016 [1]. Then, in 2017, Florida officials began noticing something strange: new cases of Zika infection in people who had traveled to Cuba.
This came as a real surprise because Cuba, unlike most other Caribbean islands, was thought to have avoided an outbreak. What’s more, by then the Zika epidemic in the Americas had slowed to a trickle, prompting the World Health Organization to delist it as a global public health emergency of international concern.
Given the Cuban observation, some wondered whether the Zika epidemic in the Americas was really over. Among them was an NIH-supported research team, including Nathan Grubaugh, Yale School of Public Health, New Haven, CT; Sharon Isern and Scott Michael, Florida Gulf Coast University, Fort Myers; and Kristian Andersen, The Scripps Research Institute, La Jolla, CA, who worked closely with the Florida Department of Health, including Andrea Morrison.
As published in Cell, the team was able to document a previously unreported outbreak in Cuba after the epidemic had seemingly ended [2]. Interestingly, another research group in Spain also recently made a similar observation about Zika in Cuba [3].
In the Cell paper, the researchers show that between June 2017 and October 2018, all but two of 155 cases—a whopping 98 percent of travel-associated Zika infections—traced back to Cuba. Further analysis suggests that the outbreak in Cuba was likely of similar magnitude to outbreaks that occurred in other Caribbean nations.
Their estimates suggest there were likely many thousands of Zika cases in Cuba, and more than 5,000 likely should have been diagnosed and reported in 2017. The only difference was the timing. The Cuban outbreak of Zika virus occurred about a year after infections subsided elsewhere in the Caribbean.
To fill in more of the blanks, the researchers relied on Zika virus genomes from nine infected Florida travelers who returned from Cuba in 2017 and 2018. The sequencing data support multiple introductions of Zika virus to Cuba from other Caribbean islands in the summer of 2016.
The outbreak peaked about a year after the virus made its way to Cuba, similar to what happened in other places. But the Cuban outbreak was likely delayed by a year thanks to an effective mosquito control campaign by local authorities, following detection of the Brazilian outbreak. While information is lacking, including whether Zika infections had caused birth defects, it’s likely those efforts were relaxed once the emergency appeared to be over elsewhere in the Caribbean, and the virus took hold.
The findings serve as yet another reminder that the Zika virus—first identified in the Zika Forest in Uganda in 1947 and for many years considered a mostly inconsequential virus [4]—has by no means been eliminated. Indeed, such unrecognized and delayed outbreaks of Zika raise the risk of travelers innocently spreading the virus to other parts of the world.
The encouraging news is that, with travel surveillance data and genomic tools —enabled by open science—it is now possible to detect such outbreaks. By combining resources and data, it will be possible to develop even more effective and responsive surveillance frameworks to pick up on emerging health threats in the future.
In the meantime, work continues to develop a vaccine for the Zika virus, with more than a dozen clinical trials underway that pursue a variety of vaccination strategies. With the Zika pandemic resolved in the Americas, these studies can be harder to conduct, since proof of efficacy is not possible without active infections. But, as this paper shows, we must remain ready for future outbreaks of this unique and formidable virus.
References:
[1] Genomic epidemiology reveals multiple introductions of Zika virus into the United States. Grubaugh et al. Nature. 2017 Jun 15;546(7658):401-405.
[2] Travel surveillance and genomics uncover a hidden Zika outbreak during the waning epidemic. Grubaugh ND, Saraf S, Gangavarapu K, Watts A, Tan AL, Oidtman RJ, Magnani DM, Watkins DI, Palacios G, Hamer DH; GeoSentinel Surveillance Network, Gardner LM, Perkins TA, Baele G, Khan K, Morrison A, Isern S, Michael SF, Andersen .KG, et. al. Cell. 2019 Aug 22;178(5):1057-1071.e11.
[3] Mirroring the Zika epidemics in Cuba: The view from a European imported diseases clinic. Almuedo-Riera A, Rodriguez-Valero N, Camprubí D, Losada Galván I, Zamora-Martinez C, Pousibet-Puerto J, Subirà C, Martinez MJ, Pinazo MJ, Muñoz J. Travel Med Infect Dis. 2019 Jul – Aug;30:125-127.
[4] Pandemic Zika: A Formidable Challenge to Medicine and Public Health. Morens DM, Fauci AS. J Infect Dis. 2017 Dec 16;216(suppl_10):S857-S859.
Links:
Video: Uncovering Hidden Zika Outbreaks (Florida Gulf Coast University, Fort Myers)
Zika Virus (National Institute of Allergy and Infectious Diseases/NIH)
Zika Virus Vaccines (NIAID)
Zika Free Florida (Florida Department of Health, Tallahassee)
Grubaugh Lab (Yale School of Public Health, New Haven, CT)
Andersen Lab (The Scripps Research Institute, La Jolla, CA)
NIH Support: National Institute of Allergy and Infectious Diseases; National Center for Advancing Translational Sciences
Yes, It’s True: There’s Fungus Among Us
Posted on by Dr. Francis Collins
Caption: A fluorescent microscope image of a human hair shaft in the skin surrounded by bacteria (purple) and fungi (blue).
Credit: Alex Valm, National Human Genome Research Institute, NIH.
Athlete’s foot, ringworm, diaper rash, dandruff, some cases of sinusitis, and vaginal yeast infections are all caused by fungi. These microscopic co-travelers live in the air, water, soil, and, so it happens, on our body. NIH researchers have just completed the first census of the fungi that live on the human body, and it’s quite a diverse collection [1].
The researchers used Q-tips and toenail clippings to sample 14 sites from 10 healthy human volunteers and then analyzed the DNA to determine the identity of the fungi in these locations. They focused on sites—like the back of the head, nostril, feet, and groin, for example—that are frequently plagued with diseases thought to be caused by fungi. (The same team of researchers took a similar approach a few years back to catalog all the bacteria that live on human skin [2].)
