Keeping an eye on polio

On the 26th of June 2019, a three-year-old girl from Lanao Del Sur started developing a limp. With her legs becoming weaker each day, she eventually became unable to keep herself upright. Days later, she was paralyzed.

If you have heard a similar story like this before, you might already have an idea what this crippling disease is, and how most countries have eradicated this ailment decades ago. In the Philippines, we were declared free from this illness 19 years ago.

But after nearly two decades, this little girl was tagged as the first confirmed case of poliomyelitis in the country. According to reports, the girl showed signs of Acute Flaccid Paralysis (AFP), the clinical syndrome referring to the onset of weakness or muscle paralysis caused by the poliovirus.

To date, there is still no medical cure found to reverse the physical damage of AFP, forcing the sufferers to live with a disability their entire lives. It is exactly for this reason that world leaders have unanimously and enthusiastically agreed to work together towards the complete eradication of polio globally. You may be wondering, how can polio—a life-threatening disease that permanently disables children— resurface time and time again?

The answer can be found in the environment.

Years of vigilance and surveillance

Prior to the polio outbreak declaration of the Department of Health (DOH) in September 2019, the Research Institute for Tropical Medicine (RITM) processed and confirmed the presence of polioviruses in several sewage and river water samples in Manila and Davao.

RITM, through its National Polio Laboratory (NPL), determined that a total of 284 out of 755 environmental samples tested positive for various types of polioviruses during the outbreak. These samples were collected from sewage treatment plants and bodies of water in 42 sites from 15 regions.

“Before we eventually saw the polio infection in the human population, we were first able to isolate and detect the polioviruses from the samples collected for environmental surveillance,” said RITM NPL Head Dr. Lea Necitas Apostol.

According to Dr. Apostol, the presence of polioviruses in the sewage and waterway systems imply that individuals are infected with polio and are shedding the virus into the environment. Infected individuals can shed the virus for several weeks, where it can spread rapidly in communities with poor sanitation and low vaccination coverage.

The circulation of polio is detected through two kinds of surveillance—AFP surveillance and environmental surveillance. AFP surveillance is the gold standard for detecting polio cases. It involves reporting children with AFP and collecting their stool samples for analysis. Environmental surveillance, meanwhile, is a supplementary activity that provides valuable information that confirms whether or not polioviruses are present in wastewater samples.

Wastewater and stool samples are collected, specifically, because individuals with polio excrete the virus through their feces. Polio spreads via the fecal-oral route. It enters the body through the mouth; multiplies in the intestines; and spreads through contact with feces or respiratory droplets.

Both of these surveillance activities are tested and analyzed solely by RITM.

Home to the National Reference Laboratory for Polio and other Enteroviruses, RITM has been at the forefront of laboratory surveillance activities for poliovirus and other enteroviruses as part of DOH’s AFP surveillance. The Institute also spearheads the establishment of a national environmental surveillance network and serves as the regional hub for environmental surveillance in the Western Pacific Region, as recognized by the World Health Organization (WHO).

Housing the only laboratory capable of isolating and detecting polioviruses, RITM has been leading the national government’s efforts towards eradicating polio in the Philippines since 1991.

Polio outbreak vis-à-vis COVID pandemic

With the poliovirus circulating in the human population and the environment, DOH, RITM and WHO implemented a massive national polio outbreak response through simultaneous mass vaccinations, intensified surveillance of individuals with symptoms of AFP, and expansion of environmental surveillance sites.

The Institute’s main responsibility in the polio outbreak response was to provide laboratory confirmation of polio from samples collected nationwide. Seemingly already a tall order, it wasn’t long before the Institute was thrust into the role of juggling the polio epidemic and the COVID-19 pandemic since 2020.

Being also the National Referral Center for Emerging and Reemerging Infectious Diseases, RITM became the primary responding laboratory to the COVID-19 pandemic. The entirety of RITM had to realign its priorities and redirect most of its resources in providing laboratory support to combat the rising number of cases and deaths brought by the coronavirus disease.

NPL is lodged in RITM’s Department of Virology. While the Department was responding to the polio outbreak, it was also activated as one of the three COVID-19 testing streams in the Institute.

In spite of this, RITM Virology Head Dr. Mayan Uy-Lumandas has continually reassured that the “laboratory activities and operations for polio and COVID-19 remains unhampered. Key NPL and Virology staff are prepared and trained to assist in the COVID-19 response and polio outbreak simultaneously.” This meant that the laboratory continues to soldier on with its simultaneous functions, a pandemic notwithstanding.

Through the Institute’s research leadership, NPL delegated the polio outbreak responsibilities among its eleven-person team using the two-pronged surveillance approach.

While the AFP team continuously tested stool specimens from AFP cases; close contact of polio-positive cases; and healthy children from across the nation; the environmental surveillance team conducted ocular visits for possible expansion of surveillance sites and collection of wastewater samples.

The AFP team tested more than 5,000 stool samples from various regions, while also lending support to the COVID-19 laboratory testing and data management in the early months of the outbreak.

Likewise, the environmental surveillance team tested more than 700 wastewater samples and successfully expanded to more environmental surveillance sites in all parts of the Philippines, despite the imposition of nationwide travel bans. From only three environmental surveillance sites in 2017, there are now 45 sites established in all regions.

Conquering polio as a nation

The rapid strengthening of surveillance activities proved critical in monitoring the course of the outbreak, and determining the success of the response. Similarly, the intensified immunization program assured no additional poliovirus infections in humans and the environment for the past 22 months.

DOH officially announced the end of the polio outbreak on 03 June 2021.

“It took an entire nation to reach every child and every possible reservoir of polio. We came together, we saw, and we conquered polio as a nation,” said Dr. Apostol as she recounts the dedication, commitment, and willpower of every polio frontliner in the 650-day long journey.

As for the story of the three-year-old girl from Lanao del Sur, RITM hopes that her battle inspires the country to contribute globally towards a polio-free world. This is possible if every Filipino would be champions of vaccination and have every child immunized with the appropriate polio vaccine and complete its recommended doses.

by Allenor Enciso, Communication and Engagement Office