Washington: Scientists, including one of Indian origin, have for the first time reported a case of a person in the US who may have contracted Zika by coming in contact with tears or sweat from a 73-year-old patient with unusually high concentration of virus in the blood.
The first Zika virus-related death in the US occurred in June this year. It is quite rare for a Zika infection to cause severe illness in adults, much less death, researchers said.
Another individual, who visited the first while in the hospital, became ill from Zika. However, the patients had done nothing that was known at the time to put people at risk for contracting the virus.
Researchers at the University of Utah School of Medicine and ARUP Laboratories in the US found an unusually high concentration of virus in the first patient's blood as being responsible for his death.
The phenomenon may also explain how the second patient may have contracted the virus by touching the tears or sweat from the primary patient, the first such documented case.
"This rare case is helping us to understand the full spectrum of the disease, and the precautions we may need to take to avoid passing the virus from one person to another in specific situations," said Sankar Swaminathan, from the University of Utah School of Medicine.
Last May, Patient 1, a 73-year-old man, travelled to southwest Mexico, a Zika-infected area, researchers said.
Eight days after returning, he started having abdominal pain and fever. By the time he was hospitalised he had low blood pressure, inflamed, watery eyes and rapid heart rate.
Patient 2 came to visit and reported wiping away Patient 1's tears and helping to reposition him in the hospital bed.
It was not long before Patient 1 slipped into septic shock, and his kidneys, lungs and other organs started to shut down. He died shortly thereafter.
Only nine other Zika-related deaths have been reported worldwide, said Swaminathan.
Seven days after Patient 1's death, Patient 2 tested positive for Zika. However, this patient only had mild symptoms that resolved within the following week.
Patient 2 had not travelled to a Zika-infected area, and reconstruction of events ruled out other known means of catching the virus.
"This case expands our appreciation for how Zika virus can potentially spread from an infected patient to a non-infected patient without sexual contact or a mosquito vector," said Marc Couturier, from ARUP Laboratories.
Researchers found that Patient 1's blood had a very high concentration of virus - 200 million particles per millilitre.
"The viral load was 100,000 times higher than what had been reported in other Zika cases, and was an unusually high amount for any infection," said Swaminathan.
This opens up the possibility that the extraordinary amount of virus overwhelmed the patient's system, and made him extremely infectious.
The study was published in the New England Journal of Medicine.