Hantavirus containable, not highly contagious: Soumya Swaminathan

Former WHO chief scientist Soumya Swaminathan has said the ongoing Hantavirus outbreak linked to a cruise ship appears “containable” as the virus requires prolonged close contact for transmission, unlike highly contagious ones like COVID-19, measles or influenza.

Swaminathan said the long incubation period of the virus —  estimated at six to eight weeks — explains why the first case on the cruise ship surfaced nearly a month after the vessel sailed in early April. “The incubation period of this virus is quite long, and this is why it took almost a month for the first person on the ship to get it,” she said.

Believing that the ship sailed on April 2-3 and the first lady got sick at the end of April, she said, the incubation period is six to eight weeks and therefore, to be on the safe side, “these people will have to be isolated till that time.”

The former World Health Organisation chief scientist said the safest strategy would be to isolate everyone who was on the ship or had close contact with infected individuals for the entire incubation window, though some countries may choose to isolate only symptomatic people.

“Some countries might say that you only isolate if you have symptoms, but a lot of countries are basically asking people to self-isolate till the incubation period is over,” she said.

She added that anyone developing symptoms during the isolation period should be immediately tested for Hantavirus infection and said strict adherence to isolation measures could effectively halt further spread. “Essentially, if you do that till the incubation period is over, then the chances of spread are basically nil,” she said.

Explaining the transmission pattern, Swaminathan said the current strain is likely the only known Hantavirus capable of spreading from human to human and that transmission so far has been linked to prolonged close physical contact.

“In the past and also in this current outbreak, transmission has been only through prolonged close personal contact. In the case of the cruise ship, it is people who have been sharing a cabin, couples who have been in close, intimate physical contact,” she said.

Swaminathan clarified that the virus is not classified as a sexually transmitted infection.

“However, the virus has been found in different biological specimens. So it is probably there in the saliva, in the blood, maybe also in the semen,” she added.

Swaminathan also said there was a “good chance” that the virus could become aerosolised because Hantavirus causes respiratory infection and pneumonia.

“Any time you have a respiratory virus, it does come out in particles when we speak, cough or even breathe. The smaller particles can become airborne and get aerosolised,” she said.

However, she stressed that the virus is significantly less transmissible than other airborne infections and does not spread through casual contact.

“It is not casual contact that can transmit it, and therefore the contact tracing and steps being taken now to isolate people are likely to be very effective,” she said.

Drawing a comparison with the COVID-19 pandemic, Swaminathan said the absence of rapid asymptomatic transmission makes containment more feasible.

“Unlike SARS-CoV-2, where there was asymptomatic transmission, and it was very rapid, this virus, it is possible to find contacts, isolate people and contain the outbreak,” she added.