Roughly 3 million COVID-19 cases in PH may have been undetected, Ateneo paper finds

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Metro Manila (CNN Philippines, August 20) — Close to three million coronavirus cases in the Philippines may have gone undetected, according to a non-peer-reviewed academic paper published on the website of Ateneo de Manila University.

Using epidemiological and statistical modeling to estimate underreporting in the Philippines, researcher Jan Frederick Cruz found that COVID-19 cases in the Philippines from April to June may have been 2,812,891 instead of the reported 34,354. Cruz said this means that only 1.22 percent of the infections were detected during that time.

“We looked at a methodology from an established paper, trying to compute for underreporting in industrial economies that became major epicenters of the COVID-19 pandemic,” Cruz said in an interview with CNN Philippines on Thursday.

Cruz’s paper also looked into the COVID-19 situation in four other Southeast Asian states using the same computations and methodology employed to determine the prevalence of the coronavirus in the Philippines.

His analysis revealed that 96 to 99 percent of infections in the Philippines, Indonesia, Malaysia, Thailand, and Singapore in the second quarter of the year may have been unconfirmed, with his calculations suggesting that Indonesia missed the most cases among the five Southeast Asian countries. But he pointed out that the high ballpark figure for Indonesia may be due to its high population, which is more than double than that of the Philippines.

According to Cruz, there was a delay in government intervention that led to the outcome the Philippines is facing. Travel restrictions were first placed in Metro Manila midnight of March 15, and travel ban was first imposed in February for people coming from mainland China, Hong Kong, and Macau.

For the Philippines, an estimated 98 percent of the infections were not discovered during the second quarter of the year, he pointed out.

Meanwhile, Thailand may have had 89,357 infections instead of the reported 1,520, and Malaysia’s estimated cases may have reached 158,237, contrary to the official tally of 6,011.

The five economies in Southeast Asia are collectively referred to as “ASEAN-5” in the research paper.


Cruz computed what he calls his “crude estimates” by multiplying the number of reported infections with the value derived from dividing the case fatality ratio or CFR of a country by the CFR of Singapore.

Singapore was used as a baseline since it has the lowest CFR among the ASEAN-5 countries.

Cruz also noted that the CFR does not account for those “who did not undergo medical diagnosis because of either immediate recovery or non-showing of serious symptoms that would necessitate formal treatment.”

"Given this assumption, the product of said ratio and the reported cases in country n is a ballpark estimate of the true extent of viral infection in that country, inclusive of underreported cases," he added.

The equation was adopted from the peer-reviewed studies published by Hien Lau and other researchers, he explained.

The researcher warned that the “conservative figures” create a false sense of complacency within the community in terms of the spread of COVID-19 and “may reduce the urgency to act among public and private stakeholders and key decision-makers.”

He added that “low detection rates undermine government efforts to formulate effective, comprehensive, and credible public health and economic policies.”

Test, trace, isolate

The findings, according to the author, reinforce the recommendation of the World Health Organization to test, trace and isolate, and for the government to devote resources to do these to avoid “long-term health and economic distress.”

He also said that “the overarching goal of this research is to use the ballpark figures to dramatize the urgency of a mass testing policy in the Philippines.”

‘Not appropriate’ to compare different health systems

Meanwhile, the Department of Health said it is incorrect to compare the country's health care system to others because of different capacities.

In a televised briefing, Health Spokesperson Maria Rosario Vergeire said Thailand has a very organized primary health care system and facilities for tourism. Singapore, even with a small population, has adequate services.

"Hindi naman po sa dinidiskwento natin ang Pilipinas, meron din po tayo naman. Kaya lang yun sa atin kasi, we are decentralized, and we have the different facilities na meron pong pakakaiba-iba ng kakayanan across the whole country... Now if you compare it with the numbers right now, tapos hindi po natin isasama yung kapasidad ng isang bansa, parang hindi naman po appropriate din yun." she said.

[Translation: We are not discounting the Philippines, because we do have facilities. But we are decentralized, and we have different facilities that have different capabilities across the whole country...

Now if you compare it with the numbers right now, and then not include the capacity of a country, that doesn't seem to be appropriate.]

“If we want to make a policy based on evidence, we have to make sure that at least the information that we are using is reflective of the true situation,” Cruz said, adding that the government should ideally test five to ten percent of the population.