Dutch, Spanish and Swiss medical experts applied slightly different criteria for discharging patients infected with Andes hantavirus during the recent outbreak on a cruise ship –  but none required a negative blood test, as this could remain positive “for months”.

This emerged during a briefing convened by the World Health Organization’s (WHO) Information Network for Epidemics (Epi-WIN) team on Tuesday, with medical experts who had treated patients.

The Netherlands had the most relaxed criteria. Two patients sought care in the Netherlands, and both were discharged after two negative saliva tests, said Karin Veldkamp, head of infection control at the University Medical Centre in Leiden, Netherlands.

“We decided that if the saliva is negative twice, that we could safely discharge the patients at home, and then we could give them additional [isolation] measures if their urine and blood are positive,” said Veldkamp, adding that advice from medical experts from Argentina and Chile, who dealt with an outbreak in 2019, had helped guide this decision.

Spain also treated two confirmed cases and managed 12 asymptomatic contacts. It required patients to have two negative PCR tests from oropharyngeal (throat) and urine samples, said Octavio Garcia, from the high-level isolation unit at the Infectious Diseases Department of Hospital Central de la Defensa in Madrid.

Switzerland’s single positive case was a 64-year-old man with other underlying conditions, said Professor Walter Zingg from the University of Zurich’s department of infectious diseases.

He was hospitalised on 4 May and discharged on 18 May after his saliva and nasopharyngeal swabs tested negative. The virus was still faintly detectable in his urine and blood.

“We decided that if the patient is clinically well, and 14 days from the beginning of the acute phase, or 21 days from the beginning of the prodromal phase, we would stop isolation without further restrictions,” said Zingg.

“We just saw him last week, and he was still positive in both full blood and in urine,” said Zingg, adding that his contacts were required to observe 42 days of self-isolation.

Garcia said that the PCR tests of the blood of both Spanish patients “were positive throughout the disease, even after clinical convalescence”.

“We know that in different studies, especially from our colleague Dr Marcela Ferres [from the University of Chile] that full blood PCR will remain positive for a long period of time, even after more than 23 days from symptoms onset,” said Garcia.

As the virus can persist in the blood and semen, the Spanish health authorities also recommended four months of safe sex practices post-discharge.

“We recommended a monthly clinical review during the first six months after discharge to detect both clinical and psychological sequelae from these patients. They will also have a monthly blood PCR until we get a negative result.”

Early phase is most dangerous

All the experts concurred that the most dangerous time for transmission of the virus was during the early stages of the disease.

Zingg said that their research indicated that the infectious period is two days before the first symptoms.

Colin Brown, the UK’s deputy head of epidemics and emerging infections, said that the UK conducted a big literature review, “looking at particular evidence of transmission dynamics”. 

“Because we know the Andes hantavirus is detectable before symptom onset or antibody development, and that transmission mostly occurs in the prodromal phase or asymptomatic phase, we assume that there’s a big respiratory transmission component, and that there could be a degree which is asymptomatic or indeed presymptomatic,” said Brown.

“We assume certainly that there is a considerable respiratory transmission component, and that is probably mostly in the symptomatic infected individuals and during their acute symptomatic episode, but there are a lot of limitations in knowledge, therefore we’ve got quite strict PPE guidance.”

Brown added that the UK has a case-by-case approach to the virus, given the variables.

However, the UK designates the hantavirus as a “high consequence infectious disease”, based on the lack of medical countermeasures and vaccines, and its high case fatality rate.

A UK citizen who flew to Johannesburg, South Africa, after leaving the cruise ship in St Helena, was the first person to be diagnosed with the virus, prompting the UK to notify the WHO of the outbreak.

US evaluates home situation

Katherine Willet, medical director of the US National Quarantine Unit in Nebraska, said her unit is using high-level PPE, “adapting some of our prior models, very similar to our approach with COVID for quarantined individuals”. 

“Some of the US-exposed citizens are quarantining at home and not in the facility, and the approach that we’re taking there obviously is going to be variable, based on their situation,” said Willet.

Evaluating their home circumstances was important, particularly their ability to isolate from other individuals in the household. 

“The most important thing is going to be making sure that there’s airborne precaution, eye protection, and skin covering for these individuals, especially if they’re going to need to come into close contact,” she added.

Meanwhile, Health and Human Services Secretary Robert F Kennedy Jr has refused to allow one of the US citizens at the National Quarantine Unit to sit out her 42-day quarantine at home, according to Inside Medicine.

Ten of the 18 US passengers on the cruise ship have been allowed to isolate at home, while seven opted to stay in the unit. But Angela Perryman’s home state of Florida has refused to implement the 24-hour surveillance required by health authorities that would allow her to isolate at home.

Last week, Dr Michael Bell, the US Centers for Disease Control and Prevention (CDC)’s quarantine medical reviewer, concluded that Perryman’s confinement was unnecessary and that home-based monitoring would be enough to protect the public.

However, Kennedy overruled this decision without giving reasons. Ironically, Kennedy and acting CDC head Dr Jay Bhattacharya were vocal critics of COVID-19 lockdowns.

Image Credits: BBC.