The Philippine Genome Center (PGC) has recently analyzed and compared the DNA sequences for all the known genomes of SARS-CoV2 obtained from Filipino COVID-19 patients. The genome is the map of all the genes in the virus. By comparing genomes, scientists can determine a family tree for SARS-CoV2 to identify related viruses of similar origin.

Using this approach, the genome scientists at the PGC have put together the most likely family tree for the SARS-CoV2 viruses in the Philippines. This family tree, also called a viral pedigree, gives us the best history we have so far for COVID-19 in our country. I should note that the viral genomes, for the most part, were obtained from patients in Metro Manila so we do not know the complete picture for the provinces. However, NCR is the engine for the pandemic in the Philippines. 

According to the genome analysis, it is likely that COVID-19 entered the Philippines 3 times. Viral samples collected in January suggest that the first wave of COVID-19 was linked to foreign visitors from China. However, this wave did not significantly impact the local pandemic in the country. 

Viral samples collected in March suggest that the second wave was triggered by the 440 Filipino crew members and 5 tourists who returned to the Philippines on February 26, 2020, after spending a month on the M/V Diamond Princess, a cruise ship which experienced an outbreak of COVID-19. On the cruise ship, 712 out of 3,711 people became infected, and 14 passengers died. 

Though the returning Filipino seamen from the Diamond Princess were quarantined at New Clark City in Capas, Tarlac for 14 days, swab samples from patients at the Philippine General Hospital in NCR several weeks later were clearly virus infections from the cruise ship. This suggests that the local community transmission in March was linked to undetected cases of COVID-19 among the seafarers. At around the same time, the entire island of Luzon was placed under Enhanced Community Quarantine (ECQ), which lasted until June 1, 2020.

Viral samples collected in June and July suggest that the third wave of COVID-19 was triggered by people who returned to the Philippines from Europe because the virus samples from this period are descended from European variants of SARS-CoV2. It is likely therefore that this third wave was instigated by returning OFWs and OFs who were allowed to enter the country once the ECQ travel ban was lifted at the beginning of June. 

The European viruses also included a more infectious mutant called the D614G variant. This would explain the explosive rise in COVID-19 cases that we experienced in the country throughout the month of July that returned NCR to MECQ in early August. This infectious D614G viral strain is still the predominant viral strain in the Philippines today. 

Strikingly, the genomic scientists at the PGC note that the absence of Diamond Princess virus samples in June and July suggest that the two-month ECQ effectively shut down spread of the original wave in March. We flattened the curve with the ECQ, but we immediately allowed it to rise again!

What does this brief history teach us about controlling the pandemic today? It is surprising that the previous two surges of COVID-19 in our country have been directly linked to cases that were imported, first from the Diamond Princess cruise ship, and then from Europe. It suggests that our quarantine and isolation procedures, especially in NCR where most foreign travelers first land, are too leaky. Infected travelers have been able to pass through them and enter the local community where they have infected others. In June and July, this triggered the enormous surge in infections that moved us back into MECQ.

At this time, the European Union and the United States are experiencing second and third waves of COVID-19, which are more substantial than the original waves of the pandemic 8 months ago. If we are not careful, returning Filipinos and balikbayans, many of whom are returning home to celebrate pasko with their families, will also bring the pandemic home with them. We have to strengthen the quarantine and isolation procedures at our borders today. 

Right now, a returning OFW or OF can leave his or her hotel quarantine after 24 hours as long as the swab test taken at the airport is negative. However, the scientific data shows that infected travelers can test negative immediately upon arrival and yet test positive several days later because they were exposed to the virus during their journey. One study published in the Annals of Internal Medicine found that the possibility of getting a false negative from a PCR swab test was 67% on the fourth day after exposure to the virus but 38% a day later. Clearly, passengers should wait 4 to 5 days before getting their swab test to minimize the chances of a false negative result.

Even if we cannot extend their initial quarantine, we need to improve our procedures so that we will be able to catch infectious travelers who test false negative at the airport. From anecdotal evidence, I know that travelers from abroad who continue to the provinces are put into immediate community quarantine by their provincial LGUs where they are monitored for 14 days. This effectively halts spread into the local community. 

However, also from anecdotal evidence, I know that travelers from abroad who live in NCR are not usually monitored. Most of them voluntarily enter into self-quarantine at home to complete the 14-day quarantine period. But I also know of many who believe that the negative swab test frees them from the obligation to self-quarantine. They do not realize that they still may be positive even though they tested negative upon arrival at NAIA. If we are not careful, they will trigger another wave of COVID-19 in the country sometime in the weeks and months ahead. 

As the American philosopher, George Santayana said in 1905, “Those who cannot remember the past are condemned to repeat it.” – Rappler.com

Reverend Fr. Nicanor Austriaco, O.P. is Visiting Professor of Biological Sciences at the University of Santo Tomas, and an OCTA Research Fellow.