Coronavirus infection without symptoms might be more common than previously thought, according to a study of people isolated on a cruise ship during the pandemic.
More than 80 per cent of the passengers and crew on the unnamed cruise ship who tested positive for COVID-19 were asymptomatic. The prevalence of the virus on affected cruise ships is therefore likely to be “significantly underestimated”, the study published in the journal Thorax concludes.
“Strategies are needed to assess and monitor all passengers to prevent community transmission after disembarkation,” the Australia-based researchers
Of the 217 passengers and crew on board, 128 tested positive for the virus and of those, 104 patients – 81 per cent – did not have symptoms.
The ship left in mid-March from Argentina for a planned 21-day cruise of the Antarctic, along a similar route taken by explorer Sir Ernest Shackleton in the early 1900s. It set sail after the global pandemic was declared by the World Health Organisation (WHO) and two of the study authors happened to be passengers, while a third was the expedition physician.
Passengers and crew were screened for COVID-19 symptoms, body temperatures were taken before boarding, and no-one who had recently travelled through countries with high infection rates at the time such as China and South Korea was allowed on.
The first recorded fever on board the ship was on day eight and the study authors said from that point all passengers were confined to their cabins and surgical masks were issued, while full personal protective equipment was used for any contact with any patients with a fever. Eight people had to be medically evacuated from the ship and the authors said there had been one death to date.
The Uruguayan government and Ministry of Health provided a “sanitary corridor” for the repatriation of 112 Australian and New Zealand passengers on day 28 and for all other passengers on day 32.
Researchers from the faculty of medicine and health sciences at Macquarie University, the oncology trials unit at Sunshine Coast University Hospital and the Royal Australian College of General Practitioners believe their study to be the first instance of complete COVID-19 testing of all passengers and crew on an isolated cruise ship during the current pandemic.
Prof Smyth said the study could have wider implications. He said: “It is difficult to find a reliable estimate of the number of COVID-positive patients who have no symptoms.
“In early March, WHO suggested the figure might be only 1 per cent, very different from the 81 per cent figure found on the cruise ship. As countries progress out of lockdown, a high proportion of infected but asymptomatic individuals may mean that a much higher percentage of the population than expected may have been infected with COVID.
“These individuals may have immunity to COVID. This demonstrates the urgent need for accurate seroprevalence studies to estimate the overall population infection rate across the globe.”
It remains unclear what level of immunity people develop once they have had COVID-19.
Two weeks ago I wrote here about a study by the La Jolla Institute for Immunology in California, which found that between 40 and 60 percent of people who had never been exposed to SARS-CoV-2 — the virus which causes COVID-19 — nevertheless seemed to develop an immune response to the disease in their T Cells. They appeared to have a cross-reactive immunity which had been gained through exposure to other coronaviruses — those which cause the common cold.
Now comes another study providing more evidence of the same phenomenon from a team at the Emerging Infectious Diseases Program from Duke-NUS Medical School in Singapore. Nine of 18 patients they studied showed an immune reaction in their T cells to a protein in SARS-CoV-2, in spite of never having been exposed to the virus.
The team also found that survivors of Sars — the novel coronavirus disease which had an outbreak in 2002/03 and then largely disappeared — possess a ‘robust’ cross-reactive immune response to SARS-CoV-2.
The Nordic countries of Denmark and Finland are reporting no increase in the spread of coronavirus since opening their respective schools, further suggesting that children are less likely to be sickened by COVID-19 and spread the virus.
Denmark began sending its children back to school on April 15, just over a month after Prime Minister Mette Frederiksen issued an extensive nationwide lockdown. They were kept spaced apart in classrooms and on playgrounds, while sanitation measures such as hand-washing stations and deep-cleaning procedures were put into place.
Similar measures were put into place in Finland to keep children from congregating in large groups. The country's education minister, Li Andersson, predicted that reopening schools would "have a minimal impact on the pandemic, but grand benefits for children."
Both countries say the pandemic has not spiked since schools re-opened. Cases and deaths in Denmark appear to have peaked in early April. Finland's infection rate appears to have peaked around the same time, though its death rate remained almost entirely flat throughout the pandemic, aside from two one-day spikes late last month.
Research over the last several months has continuously shown that children appear to be less at risk for becoming ill from COVID-19 and spreading it to others. Researchers in Australia, as well as the World Health Organization's chief scientist, eacn have said that children as a group are largely not responsible for spreading the coronavirus.
The U.S. economy shrank at an even faster pace than initially estimated in the first three months of this year with economists continuing to expect a far worse outcome in the current April-June quarter.
The Commerce Department reported Thursday that the gross domestic product, the broadest measure of economic health, fell at an annual rate of 5% in the first quarter, a bigger decline than the 4.8% drop first estimated a month ago.
It was the biggest quarterly decline since an 8.4% fall in the fourth quarter of 2008 during the depths of the financial crisis.
