Singapore’s implementation of a 14-day quarantine period is still an appropriate measure, said Singapore Democratic Party (SDP) chairman Dr Paul Tambyah.
In an interview with Lianhe Zaobao two days ago, Dr Tambyah was talking about the recent study from China which indicated that the Covid-19 virus could have an incubation period of up to 24 days.
Explaining that the incubation period refers to the time taken for the virus to invade the host’s cell, Dr Tambyah said that when the virus draws nutrients from the cells and destroys them, the body’s immune system will begin to attack the infected cells. This is what causes patients to develop symptoms later on.
A recent study based on data gathered from 1,099 patients diagnosed with the new coronavirus at 552 different hospitals in China showed that the incubation period for the virus ranged from zero to 24 days, with less than half of patients (43.8%) having a fever when they first see a doctor.
Dr Zhong Nanshan, a prominent Chinese scientist who is heading a government-appointed panel of experts to help contain the outbreak, said that these findings could help guide quarantine practice around the world, especially in targeting close contacts of Covid-19 patients.
The finding of a 24-day incubation period raised concerns that maybe the currently imposed 14-days quarantine might not be adequate as a precaution to curb the spread of the virus.
However, the study also noted that the 24 day incubation period is rare. As such, a member of the research team, Mr Guan Weijie, told Red Star News on Monday (10 February) that there is no need to prolong the isolated period for suspected patients.
The study was shared on medRxiv, a free online archive and distribution server for complete but unpublished medical papers. As the paper is yet to be peer-reviewed, the site cautions that it should not be used as a guide for clinical practice.
In his interview, Dr Tambyah gave examples of incubation periods for other coronaviruses that we’ve seen in recent history. Severe acute respiratory syndrome (SARS), he says, has an incubation period of two to seven days while for the middle east respiratory syndrome (MERS) it is two to 14 days. For the influenza virus, the incubation period from two to four days.
Dr Tambyah also explained that contact tracing data may not be 100% accurate, with some information being omitted altogether.
He elaborated, “You may think that it was A passed to B, while their last contact was probably 24 days ago. But this may be wrong because C may appear in the middle, and C might contact with A earlier than B. C Infected, then the virus passed from C to B.”
The study
Other finding from the study include that the frequency of Covid-19 cases with no fever is higher than those in SARS and MERS. So surveillance measures and case definition guidelines that focus heavily on fever detection could lead to these infected patients being missed initially.
It also found that hat relying on CT scans to identify those who might be infected with Covid-19 is not entirely reliable since only half of those who underwent CT scans showed ground-glass opacity, and only 46 percent showed bilateral patchy shadowing.
CT scans were included in the diagnostic criteria for Covid-19 in as some doctors were concerned that the nucleic acid tests (NATs) alone were producing too many false negative results.
Alarmingly, the study also showed that only 1.18 percent of patients had close or direct contact with wildlife, which is where experts believe the virus might have emerged. However, about 31.3 percent had been to Wuhan City, the epicentre of the virus, and 71.8% had close contact with those from Wuhan.
1.18 percent of patients had close or direct contact with wildlife, which is where experts believe the virus might have emerged. However, about 31.3 percent had been to Wuhan City, the epicentre of the virus, and 71.8% had close contact with those from Wuhan.
Finally, the study concluded that Covid-19 is transmitted via the conventional route of respiratory droplets and direct contract. However, it also found that 6.5 percent of 62 stool specimens tested positive for the virus, while testing of four more patients show the presence of the virus in their gastrointestinal tract, saliva, and urine.