KARACHI: More than nine out of 10 people infected with coronavirus experience no symptoms of the disease, according to a new study conducted by Aga Khan University (AKU) researchers.

Karachi has the largest number of Covid-19 cases in Pakistan and the study saw AKU faculty investigate Covid-19’s prevalence in parts of the city with high and low rates of transmission in people in April and June 2020.

They found that 95 per cent of those who tested positive for Covid-19 through blood tests — which register the presence of antibodies to fight the disease — reported feeling no symptoms of the illness such as cough, fever or sore throat. In other words, they were asymptomatic.

According to researchers, the proportion of asymptomatic cases in Pakistan is much higher than the developed world. Since asymptomatic people do not seek hospital treatment, this may help explain why Pakistan’s hospitals have not been under the same strain as hospitals in Spain and the UK.

Results also indicate that children and adolescents are just as likely to catch the disease as adults. Men and women face the same risk of being infected.

The study also confirmed a sharp rise in Covid-19 cases between April and June this year from 0.2pc to 8.7pc in low-community transmission areas such as Ibrahim Hyderi, and from 0.4pc to 15.1pc in high-community transmission sites like Safoora Goth, Faisal Cantonment, Pehlwan Goth and Dalmia/Shanti Nagar.

These results are in line with the federal government’s national seroprevalence study where antibody testing found that overall, 11pc of Pakistanis had contracted the disease.

“The sharp increase in antibody levels in an area with low reported cases indicates that the virus continues to spread unchecked in populations where testing rates are sub-optimal,” said Dr Imran Nisar, assistant professor at AKU and co-investigator on the study.

Over 2,000 participants participated in the first two phases of the study. Researchers are currently undertaking a third serosurvey and plan to do a fourth this month.

These surveys will show the impact of easing lockdowns around Eidul Azha and the impact of Muharram processions on the coronavirus transmission rate in communities.

“Antibody testing or seroprevalence provides a true picture of Covid-19 burden as they capture asymptomatic cases who represent silent carriers of the disease,” said Dr Fyezah Jehan, associate professor at AKU and co-investigator on the study. “Understanding how, when and in what types of settings, Covid-19 spreads is critical to developing effective public health and infection prevention measures to break chains of transmission.”

AKU’s Dr Nadia Ansari and Dr Mashal Amin as well as US-based international collaborators Dr Bailey Fosdick and Dr Daniel Barremore also contributed to the study.

Published in Dawn, September 9th, 2020