Covid-19: Patients with mild symptoms ‘might not be re-infected’

By VERAH OKEYO

People who have tested positive for Covid-19 and develop severe or mild symptoms show immunity against the virus and it is unlikely they will be infected a second time, scientists say.

Referring to several studies published on MedRxiv – a website where scientists post their research before they are peer-reviewed – Dr Anthony Etyang said the news offered “hope” for vaccines being developed against Covid-19. Of the 22.4 million people globally who had tested positive for coronavirus as of Thursday, there had not been a clinically confirmed case of re-infection, said Dr Etyang.

Some viruses, like the four that cause the ordinary flu (colds), can infect people over and over again, but Dr Etyang attributed this to the high mutation rates of influenza viruses. “After mutation, one is infected with a new strain of the virus and this makes it hard for the body’s immune system to recognise it,” he said.

Deadly coronaviruses

Thankfully, the three deadly coronaviruses – among them Severe Acute Respiratory Syndrome coronavirus (Sars-CoV) and Middle East Respiratory Syndrome coronavirus (Mers-CoV) – which are collectively called “ the classics”, change their appearance less readily from year to year.

The news comes as Kenya limps towards September, the month when the Ministry of Health projects will register the peak of infections.

On Saturday there were 355 new cases, which pushed the total tally of those who have tested positive for the virus to 33,118 in Kenya. The virus has killed 542 people in Kenya.

Dr Alex Greninger of the University of Washington’s School of Medicine in the US conducted studies on fishermen who were the only ones who did not get infected from their vessel because they had antibodies.

In a brief email interview with the Sunday Nation, Dr Greninger wrote: “Our study indicates that people with neutralising antibodies from prior exposure to Sars-CoV-2 are protected against the virus.”

Scientists do not know how long this immunity will last since the virus has only been around for ten months. However, looking at other coronaviruses, “it seems like immunity would last more than a year”, said Dr Greninger.

 Severely sick people

Immunologists, who monitor and study how the body defends itself against diseases,  are careful to declare there will be no re-infection, but say the decline of severely sick people in Covid-19 hotspots such as New York in the United States points to the possibility that the population was exposed to the virus.

 Dr Francis Ndung’u from the Kenya Medical Research Institute (Kemri) said this could be the reason there are fewer sick people who need medical attention in Kenya.

A Kemri-Wellcome Trust analysis of blood from Kenyans indicated that as many as a fifth of the country’s population has been exposed to the virus due to the presence of antibodies in the blood.

These studies allay the fears sparked off by a UK study that found out that, two months after infection, many of the antibodies patients developed disappeared.