HHealth officials have identified the first cases of Covid-19 in the United States, caused by a form of rapid spread of the coronavirus seen initially in South Africa, in two people in South Carolina.
Neither person has a history of travel to countries where the variant has been confirmed and there is no connection between the two people, South Carolina health officials said on Thursday. This indicates that there was some local spread of the variant after its arrival in the United States.
Thursday’s announcement means that three variants of the coronavirus that appear to be more contagious and have emerged in recent months have been documented in the United States. But, in a way, the news did not surprise experts. They had said for weeks that the variant that first appeared in South Africa, called B.1.351, was probably already in the US, but that country’s limited surveillance system for different coronavirus iterations means that the variant probably went unnoticed afterwards imported through a traveler and could even be spreading.
advertising
Earlier this week, Minnesota health officials confirmed the first Covid-19 case caused by P.1, a variant first identified in Brazil. There were a few hundred cases in the United States of variant B.1.1.7, which initially appeared in the United Kingdom.
The three variants are believed to be more transmissible than previous forms of the coronavirus and, if left unchecked, can lead to more cases by infecting more people more quickly. The Centers for Disease Control and Prevention estimates that B.1.1.7 may become the dominant form of coronavirus in the United States in March.
advertising
The three variants evolved independently – all viruses mutate and occasionally capture changes that give them a transmission advantage – but it happens to share some of the same mutations.
B.1.351 and P.1 in particular raised a different set of alarms than B.1.1.7. Studies have shown that the mutations that appear in both variants can help the virus partially evade the human immune response, perhaps making it more likely that the variants can reinfect people who have had an initial case of Covid-19.
These studies resulted in concerns that existing Covid-19 vaccines – which were designed based on previous iterations of the virus – may not be as effective against the variants. So far, it appears that vaccines have lost some of their neutralizing potency against some of the mutations seen in P.1 and B.1.351, but the immune response caused by vaccines is so powerful that injections can withstand a loss of part of their strength and at the same time, preventing people from getting sick with Covid-19.
On Monday, for example, Moderna said its injection should still be effective against B.1.351, despite the fact that the neutralizing antibodies generated by the vaccine do not recognize the shape of the virus, as well as other forms. Essentially, the injection-induced antibody response must still be powerful enough to help people ward off Covid-19. There is a question, however, whether the vaccine’s immune response will last as long against variants as previous viral iterations.
So far, studies investigating the impact of variants on vaccines have largely focused on neutralizing antibodies, but experts also note that injections also reassemble other parts of the immune system – including T cells, B cells and other types of antibodies – providing additional reasons that current vaccines should still work widely against variants.
Still, experts believe the coronavirus may one day catch a certain set of mutations that threaten vaccine efficacy, so, they say, vaccine manufacturers and regulators should begin to consider what it will take to update immunizations for the better. match the circulating forms of SARS-CoV-2, the scientific name of the coronavirus causes Covid-19.
Moderna, for example, said it was studying a reinforcement shot designed specifically to ward off B.1.351.
The most urgent concern with the variants, experts emphasize, is their infectivity. Cases in the United States remain very high, but are dropping from peaks earlier this month. If any of the variants takes off, the country could see another increase.
It will also be necessary for a larger portion of the population to be immune to the virus to slow the spread of more contagious variants, adding even more pressure to the US vaccination campaign.
Last week, scientists in the UK reported that the variant first seen there, B.1.1.7, could also be more deadly than other forms of the virus, although they are still analyzing national data.
Generally, experts really fear a virus that is more transmissible than one that is correspondingly more lethal; more infectious variants can lead to more deaths in general, even if they are not more deadly just because they result in many more cases.
But with B.1.1.7, “unfortunately, it looks like this virus can be both,” said John Edmunds of the London School of Hygiene & Tropical Medicine.