Scientists and doctors now say Kenya could be in the eye of a Covid-19 storm, estimating that the number of people exposed to the virus to be 2.7 million.
Blood samples from several places across the country show that there could be a huge gap between confirmed cases and the number of people exposed to coronavirus.
The data is contained in a study by the Kenya Medical Research Institute and Wellcome Trust.
It found that as many as 12.4 per cent of Nairobi residents could be having the virus.
With a population of about 4.5 million, it means slightly more than 550,000 city dwellers could be infected.
According to the study, the prevalence of antibodies to SARS-CoV-2 among blood donors ranged from 1.1 per cent in Uasin Gishu to 12.4 per cent in Nairobi.
Some 500,000 people in the Rift Valley and 400,000 in western Kenya could have been exposed to the virus, it adds. There is no data from the northern parts of the country.
In Kisumu, the third largest town in Kenya, some 7.5 per cent of the samples tested positive.
It means as many as 90,000 people could have been exposed to coronavirus.
The researchers relied on 2,535 blood samples donated between April 30 and June 16.
They say Kenya should expect "severe disease... though this has not yet happened".
The report does not say why this is the case though the country has reported a rising number of Covid-19 asymptomatic cases, leading to the government announcing a home-based care model "in order to stop the health system from being overwhelmed by the pandemic".
It is estimated that 78 per cent of patients are asymptomatic or have mild symptoms.
Just days ago, Health Chief Administrative Secretary Rashid Aman said the country has entered the Covid-19 peak season, starting from July through to September.
That means Kenya should brace itself for more coronavirus cases, he added.
The country had had 6,951 confirmed cases after testing 173,355 samples by Thursday.
Nairobi still leads with 3,526 cases. It is followed by Mombasa with 1,548.
In Mombasa, where chances of getting infected are the highest in the country, the study estimates that 100,000 people - or 8.6 per cent of the coastal city population - have been exposed to Covid-19.
"There is a large gap between the confirmed cases identified by rapid response teams in testing and tracing and the number of individuals in the population that we believe has been exposed, based on antibody data," the study says.
Globally, the cases have hit 11 million and more than 550,000 deaths. The number of deaths in Kenya has reached 149.
While the first Kenyan case was confirmed on March 4 and announced on March 13 by Health Cabinet Secretary Mutahi Kagwe, there are high chances that many people may have been infected and survived without realising it.
County hospitals where monitoring of pneumonia admissions is well established have not recorded high Covid-19 numbers.
It means people are not getting severely sick or are asymptomatic, the study goes on. It is the asymptomatic carriers that are a cause of worry for the government.
Information from the National Registry of Diseases shows that there was an increase of pneumonia cases from the time Kenya reported its first coronavirus case.
Pneumonia is one of the complications of severe Covid-19. Between January and early February, the number of pneumonia cases was 137,667. It then shot up dramatically to 195,504.
The pattern - an increase from January and then a plateau - is not similar for the same period in 2019.
While this latest study is important because blood donors are a convenient sample of the community, it acknowledges that "we may not be representatively sampling the country's population".
The researchers say accurate antibody testing is critical in helping determine when and how to begin restarting the economy and sending Kenyans back to work.
"Testing a sample of the population for antibodies tells us how many people have been exposed to the virus," it says.
President Uhuru Kenyatta last week said reopening the economy would depend on measures put in place to stop the spread of the deadly virus and the level of preparedness by devolved governments.
Mr Kenyatta said the decision to reopen the economy would be determined by the county government's capacity to respond to new cases of Covid-19 effectively.
The findings come at a time new global studies suggest that people testing negative for Covid-19 may still have some immunity.
Researchers at Karolinksa Institute, Sweden, found that for every person testing positive, two were found to have T-cells which identify and destroy infected cells.