Coronavirus carriers with no symptoms could spread disease, Italian study shows

Teddy Ng

The risk posed by people who have been infected with the new coronavirus but show no symptoms has been highlighted by an Italian study which suggests they carry the same viral load as symptomatic patients.

Italy reported 683 new fatalities and a further 5,210 infections on Wednesday, bringing its totals to 7,503 and almost 75,000, respectively.

An analysis of patients with Covid-19 – the disease caused by the coronavirus – in Lombardy, one of the worst affected regions in Italy, found no significant difference in viral load between those with symptoms and those without.

An earlier Chinese study in Wuhan – where the first cases of the disease were reported in December – suggested about 60 per cent of people who contracted the infection showed no symptoms.

Thousands of covert coronavirus cases ‘go under the radar in Wuhan’

The Italian research paper, available on preprint journal platform arXiv, was based on an analysis of 5,830 laboratory-confirmed cases between January 14 and March 8. Half of the cases studied were under the age of 50.

Health care workers made up 16 per cent of the infections in the study, while 47 per cent of the patients were hospitalised and 16 per cent were admitted to intensive care.

A further analysis by the Italian team of 380 patients who were confirmed to have the virus on February 21 found 17 of them were asymptomatic while in 68 cases there was no clear indication of symptoms. The viral load in both types of patients are similar.

“We did not observe significantly different viral loads in nasal swabs between symptomatic and asymptomatic subjects, suggesting the same potential for transmitting the virus,” the paper said.

The Wuhan study, published on the MedRxiv preprint platform earlier this month, estimated as many as 60 per cent of people who contracted the virus were asymptomatic or were very mild cases which were not reported to the authorities.

The estimate was based on about 26,000 laboratory-confirmed cases in the city, between December and February.

Meanwhile, the spread of the pandemic continues to accelerate, with Spain reporting 738 new deaths – a daily record. Spain, with a total death toll of 3,434, has now surpassed mainland China.

The US has reported 54,453 cases and 737 deaths, with more than half of the infections in New York.

New York Governor Andrew Cuomo said on Wednesday stringent density control measures may be working to contain the coronavirus in New York state, as the rate of hospitalisation showed early signs of abating.

Mainland China reported 67 new infections, all of them imported, bringing its total to 81,285 as of Wednesday. The National Health Commission said there were six new deaths, with total fatalities now standing at 3,287. A total of 74,051 patients have recovered.

More than three billion people are living under lockdown measures as countries around the world struggle to contain the outbreak.

World Health Organisation chief Tedros Adhanom Ghebreyesus said the strategy was buying time and reducing pressure on health systems. “But on their own, these measures will not extinguish epidemics,” he said.

“The point of these actions is to enable the more precise and targeted measures that are needed to stop transmission and save lives”.

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