Silent spreaders: Are symptom-free COVID-19 patients contagious?

Christian V. Esguerra, ABS-CBN News

Posted at May 21 2020 03:26 PM

Silent spreaders: Are symptom-free COVID-19 patients contagious? 1
Throngs of people gather around market stalls on Blumentritt Street in Manila on April 21, 2020 even as police were asked to enforce social distancing measures under the enhanced community quarantine. Fernando G. Sepe Jr., ABS-CBN News

MANILA -- Health Secretary Francisco Duque III raised eyebrows on Wednesday when he told senators there was no evidence that COVID-19 patients with no symptoms could infect others, a major concern as new coronavirus cases in the Philippines breached the 13,000 mark.

But a report by the US Centers for Disease Control and Prevention cited studies suggesting that the virus “can be transmitted by persons with pre-symptomatic or asymptomatic infection, which may meaningfully contribute to the propagation of the COVID-19 pandemic.”

Pre-symptomatic patients refer to those who tested positive for the virus then developed symptoms such as fever, dry cough, and sore throat. Those classified as asymptomatic do not develop any of the symptoms despite a positive test result.

The CDC report cited 2 models, which “suggested that a large number of persons with asymptomatic or mildly symptomatic infections were not detected by the health system and that these persons meaningfully contributed to ongoing community transmission.” 

“Transmission in the absence of symptoms reinforces the value of measures that prevent the spread of SARS-CoV-2 by infected persons who may not exhibit illness despite being infectious,” according to the CDC report.


The report clarified that such conclusions were “drawn from the literature available at the time and may change, given the rapidly evolving nature of the evidence base for asymptomatic transmission.”

Sen. Nancy Binay on Wednesday asked Duque about the possibility of asymptomatic patients acting as “silent spreaders” of the disease, of which the health chief cited the lack of evidence based on World Health Organization reports.

The WHO earlier said there had been “no documented asymptomatic transmission” as of its April 2 report.

But the international body said the absence of such finding then “does not exclude the possibility that it may occur” and “asymptomatic cases have been reported as part of contact tracing efforts in some countries.”

“Ang WHO, hanggang ngayon po, wala po silang ulat o ebidensiyang nakakalap na magpapakita na nakakahawa ang mga asymptomatic. WHO po ‘yan,” Duque told senators looking into the Philippine government’s response to the pandemic.

Muntinlupa Rep. Ruffy Biazon on Thursday tweeted: “Does the WHO have a report or proof that asymptomatics are not contagious? If none, the prudent thing would be for the DOH secretary to caution people, instead of stressing the absence of a report that asymptomatics are contagious. Duh.”

Former Bayan Muna Rep. Teodoro Casiño said Duque’s pronouncement could be “another desperate effort to justify government’s failure to conduct mass testing and build adequate quarantine facilities for persons suspected of having COVID-19 but asymptomatic.”


“It’s scary to declare that asymptomatic (patients) are not infectious,” Dr. Benjamin Co, a pediatric infectious diseases specialist, told ABS-CBN News.

“There’s a possibility that there are some silent and super spreaders among them.”

Co said the pronouncement coming from the health secretary no less would run counter to efforts to include asymptomatic people in the government’s expanded testing for COVID-19.

“It’s like you’re stepping on your own foot,” Co said.

The updated guidelines cover healthcare workers showing no symptoms but have a travel history or exposure to a confirmed COVID-19 patient. A number of companies also sought to examine returning workers using rapid anti-body test kits after quarantine measures were relaxed in some areas.

Like symptomatic patients, those showing no symptoms can still spread the virus but mainly through improper hygiene especially when sharing a common space with relatives, said Co.

Another CDC study said the “extent to which asymptomatic SARS-CoV-2 infections contribute to overall disease transmission is still unknown and warrants further study.”

The study found that all 5 family members of a symptomatic doctor in Wuhan, China were infected with the coronavirus but showed no symptoms.