The Ministry of Health has started a validation survey on Voluntary Medical Male Circumcision (VMMC) in Nyanza to help tackle the spread of HIV.
The study seeks to determine the number of circumcised males in Kisumu, Homa Bay, Siaya and Migori.
It was launched in Homa Bay Town by county chief officer for health Gerald Akeche and director Gordon Okomo.
VMMC was started in Nyanza in 2008.
Its purpose is to help curb the spread of HIV in Nyanza, which had the highest prevalence rates at over 20 per cent per county.
Dr Akeche said the survey, funded by the US government and Centers for Disease Control (CDC), will help in determining what resources to invest in the fight against HIV in Nyanza.
"When VMMC was launched a decade ago, the rate of new HIV infections started reducing so did the number of men who turned up to be circumcised. The survey will determine whether there are still men out there who need to be circumcised," he said.
The medic added that men aged between 10 and 29 years had embraced circumcision.
"Older men who are equally at risk of infection, shunned away. This is be an opportunity to know how many they are and if possible advise them to be circumcised," the chief officer said.
In the survey, trained medical personnel will examine men's genitals, after consent, for accuracy.
"If the client declines physical examination, the interviewer will not coerce them but proceed as per the protocol," Dr Akeche said.
Dr Okomo said the rate of infections in Homa Bay has reduced.