Secondary attack rate of the actual SARS-CoV-2 delta variant against naval vessels

A very interesting case report has recently appeared Travel Medicine JournalDescribes the actual secondary incidence of the delta variant of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in a single naval vessel. The findings are highly relevant to the debate about the protection provided by vaccination against the virus.

study: High incidence of 90% of SARS-CoV-2 delta variant infections in the crew of one naval vessel.. Image Credit: Corona Borealis Studio / Shutterstock

Background

The 2019 Coronavirus Disease (COVID-19) pandemic has caused multiple infectious waves in different parts of the world. Many viral mutations have also been reported, resulting in the emergence of several new strains of the virus. These include so-called alpha, beta, gamma, and delta variant of concern (VOCs) due to their improved transmissibility, antigenic escape, or pathogenic properties compared to wild-type strains. increase.

The current report sheds light on the sudden and rapid rise in control of the delta strain of the virus, using the story of spreading on a Navy vessel off the coast of Africa. Continent.

What did the study show?

A naval destroyer active in the Gulf of Guinea on the West African coast, 301 soldiers were performing a variety of missions. All soldiers were healthy and none were vaccinated with COVID-19 vaccine.

Of these,> 90% (272) were infected with the virus, especially the Delta variant. This shows the extreme infectivity of this variant compared to previous strains and the extent of spread among susceptible unvaccinated populations in close proximity to each other.

Of the 272 infected soldiers, about 77%, or 209, were developed. COVID19 Symptoms.. About 6% of infected soldiers developed symptoms that justified hospitalization. Over 2% of all cases were moderate to severely symptomatic.

The naval vessel was scheduled to depart from the South Korean port in East Asia on February 8, 2021 and head for the final location in the Gulf of Guinea, where it would carry out its mission. From June 28, 2021 to July 1, 2021, he stayed at the port of the Gulf of Guinea. The next day, the first symptoms of COVID-19 were reported.

On July 5, 2021, soldiers had to wear face masks and observe social distances. However, on July 6, six cases of delta infection were reported, expanding to 247 cases over the next 10 days. This reached a maximum of 272 on July 26, 2021.

That is, more than 90% of the ship’s crew was infected within 25 days.

Polymerase chain reaction (PCR) tests were performed on all soldiers on the ship. Samples taken from 64 soldiers underwent further genomic testing to determine mutants. Both have shown the presence of Delta Variant of Concern (VOC), which has caused the virus to spread explosively in most parts of the world in recent months.

Based on this, researchers hypothesized that 100% of the confirmed infections were due to this variant. Vaccines were not available during the mission. All crew members were flown to designated airports in South Korea by a special aircraft by July 20, 2021. All infected personnel recovered and were dismissed by August 10, 2021.

What is the impact?

Researchers have pointed out some points from this episode in an ongoing pandemic. First, delta variants affect more than 90% of the healthy unvaccinated population on board, and exposed naive unvaccinated individuals, including at least immunocompromised individuals, in addition to healthy people. It shows that the same degree of spread can be expected in the group of.

Second, research results show that most healthy people are asymptomatic or develop only mild symptoms when infected. However, about 6% required hospitalization and more than 2% developed moderate to severe symptoms.

Finally, this study shows the rate at which delta variants spread in confined space. After the first symptoms of COVID-19 were reported on board on July 2, 2021, the number surged to 247 by July 14, 2021.

Reasons advocated to explain this type of spread include very crowded conditions on board in confined space. In this situation, it is difficult to increase social distance due to multiple repeated contacts between soldiers. This could explain a secondary attack rate of over 90%.

Aerosol spread of delta virus in such crowded and poorly ventilated areas will further accelerate the spread of the virus. Both this virus and other respiratory viruses have proven to be highly contagious on board, including previous cruise ships.

Medical records and demographic data were not available for obvious reasons in this study. Nonetheless, this study reveals the transmission of this VOC in overcrowded conditions, where the potential for physical distance is limited and multiple contacts are repeated during the day among space inhabitants. I am doing it.

The outbreak of this massive infection on a single naval vessel clearly reflects the infectious characteristics of SARS-CoV-2 Delta VOCs... “