Hantavirus pulmonary syndrome is a rare, acute zoonotic disease and can be caused by any of a number of different hantaviruses. The initial zoonotic transmission is typically caused by human inhalation of infectious fluids from a rodent source. Symptoms include a prodrome of fever, fatigue and muscle aches followed by coughing, shortness of breath and gradual fluid filling of the lungs leading to hypotension and cardiopulmonary events. Mortality, particularly with Andes virus (ANDV), is high (30-50%) and generally occurs within 24-48 hours after the onset of cardiopulmonary symptoms.
An outbreak of Andes Virus (ANDV) hantavirus pulmonary syndrome occurred centered in Epuyen, Chubut Province, Argentina between November 2018 and February 2019. A total of 34 patients were infected and 11 deaths occurred. Blood specimens were obtained for 33/34 patients and RT-qPCR directed against the S gene of Andes virus was positive for all 33. Next generation sequencing yielded complete or nearly complete S,M and L ANDV genes in 27 of 28 tested specimens.
Transmission dynamics were investigated retrospectively by public health authority interviews with patients and contacts. The index case (Patient 1) was believed to be an individual who attended a birthday party whilst displaying symptoms of fever and malaise and stayed for around 90 minutes. Five further cases (patients 2-6) occurred among individuals who had been seated in close proximity to patient 1 and developed symptoms 17-24 days after the party. Patient 2 had an active social life and is thought to have transmitted the virus to 6 other patients (7, 8, 9,11,12,13) including his spouse (patient 9). Patient 9 was febrile at patient 2’s wake and 10 further patients (15-19, 22-24, 27, 30) who attended the wake became symptomatic within the following 14-40 days, only one of these patients (22) transmitted the virus to others (patients 31, 33, 34). Other onward transmissions occurred from patient 5, 8, 10, 14 and 28. Patients 1, 2 and 9 were the main sources of transmission infecting 21/33 (64%) cases. Reconstruction of some of the person-person events suggested that transmission was likely through inhalation of droplets or aerosolized virions. Interestingly, in 17/33 cases transmission from the infected person to the contact was accurately established as the first day of fever onset. The median R value was 1.19 overall, 2.12 before control measures were introduced and fell to 0.96 once measures were introduced.
Transmission was positively associated with higher viral load and compromised liver function in the infected patient, whilst severity of disease, age and time spent in hospital had no clear association with secondary transmission. In addition NGS showed that 78% of viral genomes retrieved from the patients shared a single viral haplotype that formed a central node from which 6 other haplotypes spread out. However, 5/6 of these haplotypes did not spread to any other patient and shared 99.8-100% sequence identity with the other ANDV sequences involved in the outbreak. No significant differences in single nucleotide polymorphisms or segment diversity were found between spreaders or non-spreaders. Phylogenetic analysis confirmed the outbreak was caused by a single spillover event occurring in the index case.
The article demonstrates that Andes hantavirus is able to sustain person-person transmission, if control measures are not enforced. The transmission by aerosol/droplet appears to occur in the early symptomatic stages of infection and requires close and relatively prolonged contact.
Read more here: Martinez VP et al., The New England Journal of Medicine (2020) 383: 2230-41 DOI: 10.1056/NEJMoa2009040