Abstract
BackgroundInfluenza A virus has been detected in the blood of some infected individuals, and may pose a safety concern for collection, handling and transport of specimens for epidemiological and public health investigations if infectious virus is present in samples. Furthermore the effect of storage on virus stability and infectivity has not been well studied.MethodsWe examined the stability of novel pandemic influenza A (H1N1) virus RNA when the virus was stored in phosphate buffered saline (PBS), plasma, or buffy coated blood at either room temperature or 4°C using a sensitive Taqman RT-PCR assay. We also investigated virus infectivity using the EID50 assay when virus was stored in PBS, plasma, or buffy coats isolated from blood at 4°C.ResultsViral RNA stability was affected by the matrix used for storage. The recovery of viral RNA was highest when virus was stored in PBS with lower amounts being recovered from plasma and buffy coats at either room temperature or 4°C. Incubation time did not appear to be a major factor for viral RNA stability, although there was gradual decline after longer periods post-incubation. Both sample matrix and incubation time affected virus infectivity. The decay in virus infectivity was greatest in PBS followed by buffy coats and plasma. Virus infectivity was abolished in buffy coats at day 20 post-incubation when virus concentrations were low.ConclusionThese data indicate that encapsidated viral RNA was stable overall in all three liquid matrices at room temperature or 4°C although it was most stable in PBS; virus infectivity in buffy coats at 4°C decayed in a time dependent manner while it remained unchanged in plasma. These findings have implications for storage, handling and transport of blood derived samples from influenza patients for epidemiological and laboratory investigations. It should be noted that there is little known about influenza viremia, and whether influenza viruses can be transmitted by blood or blood derived samples.
Highlights
Influenza A virus has been detected in the blood of some infected individuals, and may pose a safety concern for collection, handling and transport of specimens for epidemiological and public health investigations if infectious virus is present in samples
Viral RNA detection in virus spiked phosphate buffered saline (PBS), plasma or Buffy coat held at room temperature up to 72 h Ten fold dilutions of H1N1 virus in 10 μl of PBS starting with 3.55 × 106 to 3.55 × 104 EID50 of H1N1 virus in 10 μl of PBS were mixed with 130 μl of PBS, plasma, or buffy coat separately and held for different periods of time at room temperature
We have assessed the stability of novel pandemic influenza A (H1N1) virus in PBS, plasma and buffy coats subjected to conditions often encountered in specimen handling, transport, and storage
Summary
Influenza A virus has been detected in the blood of some infected individuals, and may pose a safety concern for collection, handling and transport of specimens for epidemiological and public health investigations if infectious virus is present in samples. The possibility of an influenza pandemic has focused attention on the epidemiology and pathophysiology of influenza, including its potential for viremia in the acute phase of infection [1]. Influenza A viruses belong to the Orthomyxoviridae family of RNA viruses. They contain eight segments of negative sense RNA [2]. In the 1960s, viremia was found in patients infected with influenza A virus in Asia [5,6]. It has been reported that pandemic influenza H1N1 RNA was detected in 14/139 patients included in a study, by RT-PCR, during May 2009 - April 2010 in Hong Kong [11]
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