There may be hundreds of thousands of COVID-19 patients without symptoms silently spreading the virus according to medical professionals in their assessment of one week into the relaxation of lockdown imposed by the federal authorities on Lagos and Ogun states as well as Abuja, the Federal Capital Territory (FCT).
The two states, Abuja and Kano State had been worst hit by coronavirus.
President Muhammadu Buhari eased the lockdown on Monday after five weeks against advice especially from the Nigerian Medical Association (NMA) that it was premature, citing daily increase in the number of new virus cases.
Kano lockdown is still in place.
Medical professionals, who spoke to Sunday Vanguard at the weekend, said asymptomatic cases (also known as silent spreaders in medical circle) hidden inside the population could be a major problem in the post-lockdown era as they will be moving around without knowing they harbour the virus and consequently spreading it.
The solution, according to the professionals, is the scaling up of tests so as to isolate such asymptomatic patients before they wreak more havoc in the system.
Expectedly, since the easing of the lockdown in Lagos and FCT on Monday, Nigerians have be trooping to the streets, banks and other public places as if nothing happened or was at stake.
The story of non-compliance to the guidelines on the ease of lockdown issued by the federal authorities, including the use of mask and maintaining social distancing in public places, is everywhere.
Residents threw caution to the wind under the guise that they were hungry and needed to eat.
The professionals feared that in densely populated states like Lagos and Kano, the effect could be devastating, hence the need for the COVID-19 response team to begin to ramp up testing for every Nigerian with or without symptoms.
Sunday Vanguard looks at the dangers asymptomatic patients pose as well as effective measures to manage it in the face of the rising number of positive cases.
Controversies abound over asymptomatic patients of COVID-19. This is not unconnected with the fact that such persons do not exhibit symptoms which sometimes bring about doubts over the status of some individuals.
Another question about asymptomatic is, can one transmit the virus without a sign of cough, fever or illness?
Experts say there is evidence that SARS-CoV-2 has the ability to spread silently.
Adjudged as a silent spreader across the world, it has become a growing concern in communities about people who are infected, yet feel generally okay and go about their daily lives, thus spreading the virus to friends, family members and strangers without knowing that they themselves have it.
Sadly, most of these cases go undetected if no medical tests are carried.
In China where COVID-19 started, according to the World Health Organization (WHO), those who tested positive without symptoms or follow-up exams confirmed that about 25 per cent continued to show no signs.
A modelling paper in science also suggests that in China before lockdown, undiscovered cases -- mainly people with "mild, limited or no symptoms" -- were less infectious than known cases but were still possibly responsible for 79 per cent of transmission, because so many of them continued to congregate or travel while contagious.
Other papers from Singapore and China suggest that pre-symptomatic cases account for six per cent to 13 per cent of transmission.
In Nigeria, infectious disease experts say the impact of asymptomatic cases may be more as carrying on tests on everyone was not feasible and the country is yet to escalate testing.
The President of Nigeria Infectious Disease Society, Prof Dimie Ogoina, said without observing social distancing and other preventive measures, many more Nigerians may get infected and some may develop asymptomatic disease if they have protective factors, particularly in densely populated states like Kano and Lagos.
Ogonia told Sunday Vanguard: "It is quite difficult to find asymptomatic cases among the general population since they do not have any symptom to warrant medical attention or suspicion for community screening, but testing everyone to detect asymptomatic cases is not feasible.
"The best strategy would have been to test everybody, but this is not feasible. Targeted approach might be preferable.
"For instance, testing of everyone living within an area considered to have an intense community transmission of COVID-19 might be helpful."
The professor, who also identified the availability of test kits and logistic issues as some of the challenges in managing asymptomatic cases, added that the best option would have been a rapid test kit that has the capacity to test many people quickly and easily at the same time and return reliable and valid results within seconds to minutes.
He regretted that, at the moment, there was no such rapid test kit, hence, health authorities and scientists across the globe, and in Nigeria, are actively exploring validation of various rapid test kits.
Ogoina recommended that government should apply intensive community testing especially in areas with high rates of community transmission to detect cases for isolation, even if they are asymptomatic, stressing that, in the absence of an effective drug or vaccine, targeted community testing and isolating may be the best strategy to slow or stop community transmission from asymptomatic cases.
"In addition to testing and isolating, people living in areas with intense community transmission, such as Lagos and Kano, among others, must make conscious effort to restrict their movements and travels except when necessary", he said.
"Everyone should observe all COVID-19 preventive measures as announced by the Federal Government and the NCDC.
"Consistent hand hygiene, respiratory hygiene and maintaining social distancing are critical.
"The Federal Government has made wearing of face mask mandatory for everyone going out in public.
"This strategy could theoretically be successful but for the widespread misuse and abuse of face mask in the country."
According to him, a lot was still not known about COVID-19 but it has been established that those with good immunity and without other health co-morbidities are less likely to have severe disease or to die from COVID-19.
The professor warned Nigerians to avoid anything that could depress their immunity, urging them to rest well, avoid stress and do not skip regular meals.
"Those who are above 60 years and have co-morbidities such as hypertension and diabetes mellitus, etc ought to be more careful and diligent in observing the COVID-19 preventive measures", Ogoina stated.
On the impact of asymptomatic cases in Nigeria, he said the reported high number of mild COVID-19 cases in the country compared to other developed countries may not be unconnected with the fact that Nigeria has a young population, with about 60 percent of the population less than 30 years of age.
The professor explained that although people likely to develop asymptomatic COVID-19 were not yet established, the majority of those identified to have an asymptomatic infection are persons younger than 50 years of age who do not have other health co-morbidities, pointing out that, good immunity appears to be a protective factor.
"The impact of asymptomatic infection to the spread of COVID-19 is not yet known. The only way to detect asymptomatic infection is to test as many people as possible even when they do not have symptoms and to isolate those who test positive", Ogoina said.
"However, there is the concern that when more testing is done, there will be no more isolation beds to keep confirmed cases.
"The federal and state governments, especially Lagos, FCT and Kano, among others, must build capacity to handle the surge of cases that will certainly arise from the ease of lockdown.
"Another strategy to consider is home isolation for asymptomatic cases using a strict enforcement protocol."
On his part, a consultant physician, Professor Olufemi Fasamade, who noted that widespread testing of the whole population was the only way to truly determine who has COVID-19, lamented the cost implications.
Noting that testing kits are in short supply in all countries, Fasamade, a former Chairman, Medical Advisory Committee, CMAC, Lagos University Teaching Hospital, LUTH, stressed that COVID -19 response team needs to ramp up testing capacity and speed of getting results of laboratory tests.
"They need to identify more isolation centres and need to train more staff and volunteers to join contact tracers and those treating cases", Fasamade said.
According to him, although many medical diseases are asymptomatic, COVID cases may also be without symptoms in about 50-75 per cent of cases which necessitates screening of confirmed cases.
He explained that with the easing of lockdown, the resumption of movements fuels community transmission as asymptomatic patients will take it from their homes to public places without knowing they did, while contact tracing also becomes harder as people are more mobile and contacts of each case become extremely large number and unmanageable
Te consultant noted that whereas every person is at risk, those who are frail like the elderly and have diseases are more vulnerable to picking it and dying from it.
"People with cancer, HIV/AIDS, diabetes, heart disease, malnutrition, etc will be more vulnerable", he said.
"Densely packed population groups are most vulnerable hence the larger numbers in the urban cities like Lagos, Kano and FCT are vulnerable".