A study by the US Centers for Disease Control and Prevention (CDC) has revealed that screening travellers for Covid-19 symptoms did not yield the expected results at US airports.

CDC started entry screening at designated airports for passengers from certain countries in a bid to minimise the importation of Covid-19 cases in the US and contain the spread within states.

According to CDC, a total of 766,044 travellers were screened during the period between January 17 and September 13. Of these, 298 met the criteria for public health assessment and 35 were tested for SARS-CoV-2, of which nine tested positive.

CDC said that the low case detection rate of this resource-intensive programme highlighted the need for fundamental change in the US border health strategy.

Among other things, a relatively long incubation period and travellers who might deny symptoms or take steps to avoid the detection of illness, have led to the low detection of cases.

The agency also noted that symptom-based screening programmes are ineffective for case detection as SARS-CoV-2 infection and transmission can take place in the absence of symptoms. In addition, Covid-19 symptoms can be nonspecific, making it hard to identify the cases.

Due to data collection challenges, CDC shared contact information of local health departments for 68% of the screened passengers. The report said that some states opted out of receiving data.

CDC said it concluded the programme on 14 September and decided to focus on communicating more with travellers to promote the recommended preventive measures against the coronavirus disease.