1 year on, what we do know and still don't know about COVID-19

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A worker in a protective suit is seen at a closed seafood market in Wuhan, Hubei province, China on Jan. 10, 2020. Photo by: Reuters

MANILA — Dec. 31 marks one year since the World Health Organization was alerted of atypical pneumonia cases in Wuhan, China. Since then, the disease has been identified as new coronavirus COVID-19, and diagnostics, treatments, and vaccines have been developed to help reduce disease mortality and transmission.

But while experts have gained a significant amount of knowledge of the virus, there is still a lot that is unclear and requires further evidence and research. That includes the virus’ origin, and when and how it actually jumped from animal to human.

COVID-19 — a timeline of the coronavirus outbreak

The latest developments in the pandemic.

Months since its first discovery in a wet market in Wuhan, there have been studies of the virus being present much earlier in other countries, such as Italy, or theories that it leaked from the Wuhan Institute of Virology, a biosafety lab.

In a press briefing in early December, WHO emergencies director Dr. Mike Ryan said there are many hypotheses regarding the origin and evolution of COVID-19, but those hypotheses need to be backed by data.

“They [hypotheses] all make for great stories, but at the moment there is no proof that any of the hypotheses for generation or for transmission are so,” he said.

A WHO-led mission composed of international experts is expected to shed light on these questions. Babatunde Olowokure, regional emergencies director of WHO in Western Pacific, said in a press briefing on Dec. 17 that discussions are ongoing regarding the visit and that it is anticipated to take place in early January 2021.

Scientists and health experts will continue to have their work cut out in the coming year, from tracking the origins of the virus and reconstructing what happened to finding evidence and filling knowledge gaps on COVID-19's transmission, and it's long-term health impacts.

Continuing debate over COVID-19’s airborne transmission

Another point of contention in scientific circles is the question of how much airborne particles are contributing to the spread of COVID-19. A group of scientists and engineers continue to argue that airborne transmission of SARS-CoV-2, the virus causing COVID-19, is happening on a much larger scale and should receive commensurate attention in scientific guidance and policy recommendations.

But WHO and the U.S. Centers for Disease Control and Prevention maintain that while airborne transmission of SARS-CoV-2 can occur in special circumstances — for example during medical procedures that generate aerosols such as intubation — most COVID-19 infections are still spread through respiratory droplets, which are expelled when a person coughs or sneezes, for example. 

Respiratory droplets are larger in diameter than aerosol particles. Because of their relative lightness and size, aerosol particles can linger in the air and travel distances. WHO says evaluations continue as to whether the virus can also spread outside of this type of medical procedures.

A recent editorial by The Lancet Respiratory Medicine called for embracing new research on transmission “so that clearer and more effective infection control guidance can be provided in the face of pandemic fatigue.”

Most current COVID-19 guidelines are based on the SARS-CoV-2 virus being primarily transmitted through large droplets, despite growing evidence of airborne transmission of smaller particles SARS-CoV-2 as a possible route for some viral transmission, Dr. Diana Stanley, deputy editor of The Lancet Respiratory Medicine, told Devex via email.

“If these smaller particles prove to be a means for transmission, this could have major implications for public health messaging, particularly for social distancing, as airborne particles stay in the air longer and can travel longer distances,” she said.

Meanwhile, it is now understood that people infected with COVID-19 also transmit the virus during their pre-symptomatic stages, or before they develop symptoms of the disease. People who never develop symptoms can also transmit the virus, but the extent to which this occurs need further research, according to WHO.

A question on vaccines and herd immunity

The speed with which vaccines have been developed for COVID-19 has been widely acknowledged by the scientific community. But there remain a lot of unknowns when it comes to the COVID-19 vaccines currently being rolled out and those in development. This includes whether vaccinated individuals can transmit the virus to others, and how long can vaccines induce immunity and protect people from getting infected with COVID-19.

COVID-19 vaccines are a scientific feat — but lower-income nations are still fighting for equity

As an additional set of higher-income countries are expected to roll out COVID-19 vaccines to their at-risk populations, many lower-income countries remain uncertain for when high-risk members of their populations will also get their first vaccine shots.

Other pertinent questions include whether vaccine booster doses will be needed, and whether virus mutations will demand regular changes in the vaccine and repeated vaccinations, said Dr. Márcio Silveira da Fonseca, infectious diseases medical adviser for Médecins Sans Frontières - Access Campaign, who argued that learning these will take time.

The recent virus mutation reported in the United Kingdom, which points to an increase in the risk of transmission of the virus based on preliminary data, has also raised questions on the impact of such mutations on COVID-19 vaccines.

Uncertainties over these questions have in turn affected the ability to estimate herd immunity thresholds, which is not an easy calculation itself.

“It [herd immunity] takes into account parameters [such] as the intensity of transmission and, depending on the parameters and assumptions used for calculation, one can get to very different numbers,” Silveira da Fonseca said, adding that the threshold for herd immunity will also depend on population behavior.

“We should not rely on a single number. An overall high rate of vaccine coverage does not imply that we are all safe.”

— Babatunde Olowokure, regional emergencies director of WHO in Western Pacific

The limited supply of vaccines also means it will take a while before a form of herd immunity can be achieved. Outbreaks of COVID-19 can happen if there are pockets of the population with lower vaccination coverage, he said. This is evident with measles, where outbreaks appeared in communities with poor access to health services or in communities with a high proportion of people who are skeptical of vaccination.

“And finally, we must remember that [COVID-19] vaccine efficacy is not 100%, so some will simply not develop immunity, raising the threshold of the proportion to be vaccinated,” the MSF medical adviser said.

Instead of focusing on an overall statistic in calculating herd immunity threshold for COVID-19, WHO’s Olowokure said “we should take advantage of our knowledge of COVID-19 transmission to have a smart and targeted approach.”

“We should not rely on a single number. An overall high rate of vaccine coverage does not imply that we are all safe,” he said.

COVID-19’s lingering health impacts

Understanding the longer term health impacts of COVID-19 on infected individuals is also crucial. While data show the majority of people who get COVID-19 recover from it, some of them suffer from lingering symptoms such as fatigue and headache for weeks or months, and others develop complications that put them at risk for long-term health impacts such as heart, renal, and lung disease.

But it will take years to understand the full impact of COVID-19 on people’s health, said Dr. Syra Madad, senior director of the systemwide special pathogens program at NYC Health + Hospitals.

World hits 1M COVID-19 deaths. How did we get here, and will it get worse?

"One million is a terrible number. And I think we need to reflect on that, before we start considering the second million," says Dr. Michael Ryan, executive director of the WHO Health Emergencies Programme.

“People think that COVID-19 is … not a deadly disease, and that only 1% of people that catch it died. And I think it's really important to understand that, while the rate of death may not be significant in terms of the case fatality rate, the impact that it has on the human body after infection is something that absolutely people need to … take into consideration,” she said, referring to the U.S. situation.

“Because when you get infected, we know that at least 1% of people [in the United States] will die from COVID-19, another 10[%] to 20% will be hospitalized, and … an upwards of 32[%] to 35% or more will have long lasting symptoms from COVID-19. And that puts them at potentially increased risk for different health issues,” she added.

COVID-19 recovery centers are now being established in different parts of the United States, including in New York City, to act as a one-stop-shop for patients suffering from longer term effects of the disease, and a lot of these centers are located in some of the hardest hit communities infected with COVID-19, Madad said.

One of the challenges is knowing how many people are experiencing lingering health effects of COVID-19. People who may have been infected with the virus but never received confirmatory testing may already be experiencing longer term COVID-19 symptoms, but attributing them to something else.

Dr. Javed Ali, International Medical Corps director of emergency response, told Devex over email the organization provides follow-up care to patients in its supported health facilities in different parts of the world, including maternal health care, gender-based violence services, and nutrition services.

“However, we haven’t seen enough of the long-term impact of COVID-19 to truly measure it yet. We don’t have enough data to know what follow up will be required. When we do, we will provide it to the best of our ability,” he said.

Pregnant women infected with COVID-19 are also identified to be at higher risk for severe disease, or hospitalization, but there remain more questions than answers on the effect of COVID-19 on this particular population, Madad said.

The same applies to whether pregnant women might pass on the infection to their unborn child. No active form of the virus has been found in fluid samples around the baby in the womb or in breastmilk to date, according to information from WHO published last September.

“This has been a historic scientific achievement in the sense that we have learned so much about a disease ... in a very short period of time. But there still is a lot more that we don't know. And ... we'll only learn about it as time progresses," Madad said.

About the author

  • Jenny Lei Ravelo

    Jenny Lei Ravelo is a Devex Senior Reporter based in Manila. She covers global health, with a particular focus on the World Health Organization, and other development and humanitarian aid trends in Asia Pacific. Prior to Devex, she wrote for ABS-CBN, one of the largest broadcasting networks in the Philippines, and was a copy editor for various international scientific journals. She received her journalism degree from the University of Santo Tomas.